diff --git a/pkgs/applications/virtualization/xen/packages.nix b/pkgs/applications/virtualization/xen/packages.nix
index 8f5262acb024..f4bde18f3df6 100644
--- a/pkgs/applications/virtualization/xen/packages.nix
+++ b/pkgs/applications/virtualization/xen/packages.nix
@@ -10,8 +10,6 @@ rec {
   xen_4_5-vanilla = callPackage ./4.5.nix {
     # At the very least included seabios and etherboot need gcc49,
     # so we have to build all of it with gcc49.
-    stdenv = overrideCC stdenv gcc49;
-
     meta = {
       description = "vanilla";
       longDescription = ''
@@ -60,8 +58,6 @@ rec {
   xen_4_8-vanilla = callPackage ./4.8.nix {
     # At the very least included seabios and etherboot need gcc49,
     # so we have to build all of it with gcc49.
-    stdenv = overrideCC stdenv gcc49;
-
     meta = {
       description = "vanilla";
       longDescription = ''
diff --git a/pkgs/build-support/cc-wrapper/add-flags.sh b/pkgs/build-support/cc-wrapper/add-flags.sh
index 1edfe8bfc753..4d28ba08d103 100644
--- a/pkgs/build-support/cc-wrapper/add-flags.sh
+++ b/pkgs/build-support/cc-wrapper/add-flags.sh
@@ -1,37 +1,88 @@
+# N.B. It may be a surprise that the derivation-specific variables are exported,
+# since this is just sourced by the wrapped binaries---the end consumers. This
+# is because one wrapper binary may invoke another (e.g. cc invoking ld). In
+# that case, it is cheaper/better to not repeat this step and let the forked
+# wrapped binary just inherit the work of the forker's wrapper script.
+
+var_templates=(
+    NIX_CC_WRAPPER+START_HOOK
+    NIX_CC_WRAPPER+EXEC_HOOK
+    NIX_LD_WRAPPER+START_HOOK
+    NIX_LD_WRAPPER+EXEC_HOOK
+
+    NIX+CFLAGS_COMPILE
+    NIX+CFLAGS_LINK
+    NIX+CXXSTDLIB_COMPILE
+    NIX+CXXSTDLIB_LINK
+    NIX+GNATFLAGS_COMPILE
+    NIX+IGNORE_LD_THROUGH_GCC
+    NIX+LDFLAGS
+    NIX+LDFLAGS_BEFORE
+    NIX+LDFLAGS_AFTER
+    NIX+LDFLAGS_HARDEN
+
+    NIX+SET_BUILD_ID
+    NIX+DONT_SET_RPATH
+    NIX+ENFORCE_NO_NATIVE
+)
+
+# Accumulate infixes for taking in the right input parameters. See setup-hook
+# for details.
+declare -a role_infixes=()
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD:-}" ]; then
+    role_infixes+=(_BUILD_)
+fi
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST:-}" ]; then
+    role_infixes+=(_)
+fi
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_TARGET:-}" ]; then
+    role_infixes+=(_TARGET_)
+fi
+
+# We need to mangle names for hygiene, but also take parameters/overrides
+# from the environment.
+for var in "${var_templates[@]}"; do
+    outputVar="${var/+/_@infixSalt@_}"
+    export ${outputVar}+=''
+    # For each role we serve, we accumulate the input parameters into our own
+    # cc-wrapper-derivation-specific environment variables.
+    for infix in "${role_infixes[@]}"; do
+        inputVar="${var/+/${infix}}"
+        if [ -v "$inputVar" ]; then
+            export ${outputVar}+="${!outputVar:+ }${!inputVar}"
+        fi
+    done
+done
+
 # `-B@out@/bin' forces cc to use ld-wrapper.sh when calling ld.
-export NIX_CFLAGS_COMPILE="-B@out@/bin/ $NIX_CFLAGS_COMPILE"
+NIX_@infixSalt@_CFLAGS_COMPILE="-B@out@/bin/ $NIX_@infixSalt@_CFLAGS_COMPILE"
 
 # Export and assign separately in order that a failing $(..) will fail
 # the script.
 
 if [ -e @out@/nix-support/libc-cflags ]; then
-    export NIX_CFLAGS_COMPILE
-    NIX_CFLAGS_COMPILE="$(< @out@/nix-support/libc-cflags) $NIX_CFLAGS_COMPILE"
+    NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/libc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/cc-cflags ]; then
-    export NIX_CFLAGS_COMPILE
-    NIX_CFLAGS_COMPILE="$(< @out@/nix-support/cc-cflags) $NIX_CFLAGS_COMPILE"
+    NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/cc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/gnat-cflags ]; then
-    export NIX_GNATFLAGS_COMPILE
-    NIX_GNATFLAGS_COMPILE="$(< @out@/nix-support/gnat-cflags) $NIX_GNATFLAGS_COMPILE"
+    NIX_@infixSalt@_GNATFLAGS_COMPILE="$(< @out@/nix-support/gnat-cflags) $NIX_@infixSalt@_GNATFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags ]; then
-    export NIX_LDFLAGS
-    NIX_LDFLAGS+=" $(< @out@/nix-support/libc-ldflags)"
+    NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/libc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/cc-ldflags ]; then
-    export NIX_LDFLAGS
-    NIX_LDFLAGS+=" $(< @out@/nix-support/cc-ldflags)"
+    NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/cc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags-before ]; then
-    export NIX_LDFLAGS_BEFORE
-    NIX_LDFLAGS_BEFORE="$(< @out@/nix-support/libc-ldflags-before) $NIX_LDFLAGS_BEFORE"
+    NIX_@infixSalt@_LDFLAGS_BEFORE="$(< @out@/nix-support/libc-ldflags-before) $NIX_@infixSalt@_LDFLAGS_BEFORE"
 fi
 
-export NIX_CC_WRAPPER_FLAGS_SET=1
+# That way forked processes will not extend these environment variables again.
+export NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET=1
diff --git a/pkgs/build-support/cc-wrapper/add-hardening.sh b/pkgs/build-support/cc-wrapper/add-hardening.sh
index c91ff0a9d0bd..aa8eb720486c 100644
--- a/pkgs/build-support/cc-wrapper/add-hardening.sh
+++ b/pkgs/build-support/cc-wrapper/add-hardening.sh
@@ -1,67 +1,69 @@
 hardeningFlags=(fortify stackprotector pic strictoverflow format relro bindnow)
-# Intentionally word-split in case 'hardeningEnable' is defined in Nix.
-hardeningFlags+=(${hardeningEnable[@]})
+# Intentionally word-split in case 'hardeningEnable' is defined in
+# Nix. Also, our bootstrap tools version of bash is old enough that
+# undefined arrays trip `set -u`.
+if [[ -v hardeningEnable[@] ]]; then
+  hardeningFlags+=(${hardeningEnable[@]})
+fi
 hardeningCFlags=()
 hardeningLDFlags=()
 
 declare -A hardeningDisableMap
 
-# Intentionally word-split in case 'hardeningDisable' is defined in Nix. The
-# array expansion also prevents undefined variables from causing trouble with
-# `set -u`.
-for flag in ${hardeningDisable[@]} @hardening_unsupported_flags@
+# Intentionally word-split in case 'hardeningDisable' is defined in Nix.
+for flag in ${hardeningDisable[@]:-IGNORED_KEY} @hardening_unsupported_flags@
 do
   hardeningDisableMap[$flag]=1
 done
 
-if [[ -n "$NIX_DEBUG" ]]; then
+if [[ -n "${NIX_DEBUG:-}" ]]; then
   printf 'HARDENING: disabled flags:' >&2
   (( "${#hardeningDisableMap[@]}" )) && printf ' %q' "${!hardeningDisableMap[@]}" >&2
   echo >&2
 fi
 
-if [[ -z "${hardeningDisableMap[all]}" ]]; then
-  if [[ -n "$NIX_DEBUG" ]]; then
+if [[ -z "${hardeningDisableMap[all]:-}" ]]; then
+  if [[ -n "${NIX_DEBUG:-}" ]]; then
     echo 'HARDENING: Is active (not completely disabled with "all" flag)' >&2;
   fi
   for flag in "${hardeningFlags[@]}"
   do
-    if [[ -z "${hardeningDisableMap[$flag]}" ]]; then
+    if [[ -z "${hardeningDisableMap[$flag]:-}" ]]; then
       case $flag in
         fortify)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling fortify >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling fortify >&2; fi
           hardeningCFlags+=('-O2' '-D_FORTIFY_SOURCE=2')
           ;;
         stackprotector)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling stackprotector >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling stackprotector >&2; fi
           hardeningCFlags+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
           ;;
         pie)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling CFlags -fPIE >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling CFlags -fPIE >&2; fi
           hardeningCFlags+=('-fPIE')
           if [[ ! ("$*" =~ " -shared " || "$*" =~ " -static ") ]]; then
-            if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling LDFlags -pie >&2; fi
+            if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling LDFlags -pie >&2; fi
             hardeningLDFlags+=('-pie')
           fi
           ;;
         pic)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling pic >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling pic >&2; fi
           hardeningCFlags+=('-fPIC')
           ;;
         strictoverflow)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling strictoverflow >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling strictoverflow >&2; fi
           hardeningCFlags+=('-fno-strict-overflow')
           ;;
         format)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling format >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling format >&2; fi
           hardeningCFlags+=('-Wformat' '-Wformat-security' '-Werror=format-security')
           ;;
         relro)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling relro >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling relro >&2; fi
           hardeningLDFlags+=('-z' 'relro')
           ;;
         bindnow)
-          if [[ -n "$NIX_DEBUG" ]]; then echo HARDENING: enabling bindnow >&2; fi
+          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling bindnow >&2; fi
           hardeningLDFlags+=('-z' 'now')
           ;;
         *)
diff --git a/pkgs/build-support/cc-wrapper/cc-wrapper.sh b/pkgs/build-support/cc-wrapper/cc-wrapper.sh
index 966556566077..e5a3a5818519 100644
--- a/pkgs/build-support/cc-wrapper/cc-wrapper.sh
+++ b/pkgs/build-support/cc-wrapper/cc-wrapper.sh
@@ -1,5 +1,5 @@
 #! @shell@
-set -e -o pipefail
+set -eu -o pipefail
 shopt -s nullglob
 
 path_backup="$PATH"
@@ -11,12 +11,12 @@ if [[ -n "@coreutils_bin@" && -n "@gnugrep_bin@" ]]; then
     PATH="@coreutils_bin@/bin:@gnugrep_bin@/bin"
 fi
 
-if [ -n "$NIX_CC_WRAPPER_START_HOOK" ]; then
-    source "$NIX_CC_WRAPPER_START_HOOK"
+if [ -z "${NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET:-}" ]; then
+    source @out@/nix-support/add-flags.sh
 fi
 
-if [ -z "$NIX_CC_WRAPPER_FLAGS_SET" ]; then
-    source @out@/nix-support/add-flags.sh
+if [ -n "$NIX_CC_WRAPPER_@infixSalt@_START_HOOK" ]; then
+    source "$NIX_CC_WRAPPER_@infixSalt@_START_HOOK"
 fi
 
 source @out@/nix-support/utils.sh
@@ -36,7 +36,7 @@ declare -i n=0
 nParams=${#params[@]}
 while [ "$n" -lt "$nParams" ]; do
     p=${params[n]}
-    p2=${params[n+1]}
+    p2=${params[n+1]:-} # handle `p` being last one
     if [ "$p" = -c ]; then
         dontLink=1
     elif [ "$p" = -S ]; then
@@ -63,7 +63,7 @@ while [ "$n" -lt "$nParams" ]; do
         nonFlagArgs=1
     elif [ "$p" = -m32 ]; then
         if [ -e @out@/nix-support/dynamic-linker-m32 ]; then
-            NIX_LDFLAGS+=" -dynamic-linker $(< @out@/nix-support/dynamic-linker-m32)"
+            NIX_@infixSalt@_LDFLAGS+=" -dynamic-linker $(< @out@/nix-support/dynamic-linker-m32)"
         fi
     fi
     n+=1
@@ -79,13 +79,13 @@ if [ "$nonFlagArgs" = 0 ]; then
 fi
 
 # Optionally filter out paths not refering to the store.
-if [[ "$NIX_ENFORCE_PURITY" = 1 && -n "$NIX_STORE" ]]; then
+if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "$NIX_STORE" ]]; then
     rest=()
     nParams=${#params[@]}
     declare -i n=0
     while [ "$n" -lt "$nParams" ]; do
         p=${params[n]}
-        p2=${params[n+1]}
+        p2=${params[n+1]:-} # handle `p` being last one
         if [ "${p:0:3}" = -L/ ] && badPath "${p:2}"; then
             skip "${p:2}"
         elif [ "$p" = -L ] && badPath "$p2"; then
@@ -106,7 +106,7 @@ fi
 
 
 # Clear march/mtune=native -- they bring impurity.
-if [ "$NIX_ENFORCE_NO_NATIVE" = 1 ]; then
+if [ "$NIX_@infixSalt@_ENFORCE_NO_NATIVE" = 1 ]; then
     rest=()
     for p in "${params[@]}"; do
         if [[ "$p" = -m*=native ]]; then
@@ -120,36 +120,36 @@ fi
 
 if [[ "$isCpp" = 1 ]]; then
     if [[ "$cppInclude" = 1 ]]; then
-        NIX_CFLAGS_COMPILE+=" ${NIX_CXXSTDLIB_COMPILE-@default_cxx_stdlib_compile@}"
+        NIX_@infixSalt@_CFLAGS_COMPILE+=" ${NIX_@infixSalt@_CXXSTDLIB_COMPILE-@default_cxx_stdlib_compile@}"
     fi
-    NIX_CFLAGS_LINK+=" $NIX_CXXSTDLIB_LINK"
+    NIX_@infixSalt@_CFLAGS_LINK+=" $NIX_@infixSalt@_CXXSTDLIB_LINK"
 fi
 
 source @out@/nix-support/add-hardening.sh
 
 # Add the flags for the C compiler proper.
-extraAfter=($NIX_CFLAGS_COMPILE "${hardeningCFlags[@]}")
+extraAfter=($NIX_@infixSalt@_CFLAGS_COMPILE "${hardeningCFlags[@]}")
 extraBefore=()
 
 if [ "$dontLink" != 1 ]; then
 
     # Add the flags that should only be passed to the compiler when
     # linking.
-    extraAfter+=($NIX_CFLAGS_LINK "${hardeningLDFlags[@]}")
+    extraAfter+=($NIX_@infixSalt@_CFLAGS_LINK "${hardeningLDFlags[@]}")
 
     # Add the flags that should be passed to the linker (and prevent
-    # `ld-wrapper' from adding NIX_LDFLAGS again).
-    for i in $NIX_LDFLAGS_BEFORE; do
+    # `ld-wrapper' from adding NIX_@infixSalt@_LDFLAGS again).
+    for i in $NIX_@infixSalt@_LDFLAGS_BEFORE; do
         extraBefore+=("-Wl,$i")
     done
-    for i in $NIX_LDFLAGS; do
+    for i in $NIX_@infixSalt@_LDFLAGS; do
         if [ "${i:0:3}" = -L/ ]; then
             extraAfter+=("$i")
         else
             extraAfter+=("-Wl,$i")
         fi
     done
-    export NIX_LDFLAGS_SET=1
+    export NIX_@infixSalt@_LDFLAGS_SET=1
 fi
 
 # As a very special hack, if the arguments are just `-v', then don't
@@ -162,18 +162,21 @@ if [ "$*" = -v ]; then
 fi
 
 # Optionally print debug info.
-if [ -n "$NIX_DEBUG" ]; then
+if [ -n "${NIX_DEBUG:-}" ]; then
+    set +u # Old bash workaround, see ld-wrapper for explanation.
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2
     printf "  %q\n" "${params[@]}" >&2
     echo "extra flags after to @prog@:" >&2
     printf "  %q\n" "${extraAfter[@]}" >&2
+    set -u
 fi
 
-if [ -n "$NIX_CC_WRAPPER_EXEC_HOOK" ]; then
-    source "$NIX_CC_WRAPPER_EXEC_HOOK"
+if [ -n "$NIX_CC_WRAPPER_@infixSalt@_EXEC_HOOK" ]; then
+    source "$NIX_CC_WRAPPER_@infixSalt@_EXEC_HOOK"
 fi
 
 PATH="$path_backup"
+set +u # Old bash workaround, see above.
 exec @prog@ "${extraBefore[@]}" "${params[@]}" "${extraAfter[@]}"
diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix
index e0cc1fc26696..01d1bbd7a5d5 100644
--- a/pkgs/build-support/cc-wrapper/default.nix
+++ b/pkgs/build-support/cc-wrapper/default.nix
@@ -53,42 +53,13 @@ let
     "-isystem $(echo -n ${cc.gcc}/include/c++/*) -isystem $(echo -n ${cc.gcc}/include/c++/*)/$(${cc.gcc}/bin/gcc -dumpmachine)";
 
   dashlessTarget = stdenv.lib.replaceStrings ["-"] ["_"] targetPlatform.config;
-  # TODO(@Ericson2314) Make unconditional
-  infixSalt  = stdenv.lib.optionalString (targetPlatform != hostPlatform) dashlessTarget;
-  infixSalt_ = stdenv.lib.optionalString (targetPlatform != hostPlatform) (dashlessTarget + "_");
-  _infixSalt = stdenv.lib.optionalString (targetPlatform != hostPlatform) ("_" + dashlessTarget);
 
-  # We want to prefix all NIX_ flags with the target triple
-  preWrap = textFile:
-    # TODO: Do even when not cross on next mass-rebuild
-    # TODO: use @target_tripple@ for consistency
-    if targetPlatform == hostPlatform
-    then textFile
-    else runCommand "sed-nix-env-vars" {} (''
-      cp --no-preserve=mode ${textFile} $out
-
-      sed -i $out \
-        -e 's^NIX_^NIX_${infixSalt_}^g' \
-        -e 's^addCVars^addCVars${_infixSalt}^g' \
-        -e 's^\[ -z "\$crossConfig" \]^\[\[ "${builtins.toString (targetPlatform != hostPlatform)}" || -z "$crossConfig" \]\]^g'
-
-      # NIX_ things which we don't both use and define, we revert them
-      #asymmetric=$(
-      #  for pre in "" "\\$"
-      #  do
-      #    grep -E -ho $pre'NIX_[a-zA-Z_]*' ./* | sed 's/\$//' | sort | uniq
-      #  done | sort | uniq -c | sort -nr | sed -n 's/^1 NIX_//gp')
-
-      # hard-code for now
-      asymmetric=("CXXSTDLIB_COMPILE" "CC")
-
-      # The ([^a-zA-Z_]|$) bussiness is to ensure environment variables that
-      # begin with `NIX_CC` don't also get blacklisted.
-      for var in "''${asymmetric[@]}"
-      do
-        sed -i $out -E -e "s~NIX_${infixSalt_}$var([^a-zA-Z_]|$)~NIX_$var\1~g"
-      done
-    '');
+  # The "infix salt" is a arbitrary string added in the middle of env vars
+  # defined by cc-wrapper's hooks so that multiple cc-wrappers can be used
+  # without interfering. For the moment, it is defined as the target triple,
+  # adjusted to be a valid bash identifier. This should be considered an
+  # unstable implementation detail, however.
+  infixSalt = dashlessTarget;
 
   # The dynamic linker has different names on different platforms. This is a
   # shell glob that ought to match it.
@@ -129,20 +100,21 @@ stdenv.mkDerivation {
   gnugrep_bin = if nativeTools then "" else gnugrep;
 
   binPrefix = prefix;
+  inherit infixSalt;
 
   passthru = {
     inherit libc nativeTools nativeLibc nativePrefix isGNU isClang default_cxx_stdlib_compile
-            prefix infixSalt infixSalt_ _infixSalt;
+            prefix;
 
     emacsBufferSetup = pkgs: ''
       ; We should handle propagation here too
       (mapc (lambda (arg)
         (when (file-directory-p (concat arg "/include"))
-          (setenv "NIX_${infixSalt_}CFLAGS_COMPILE" (concat (getenv "NIX_${infixSalt_}CFLAGS_COMPILE") " -isystem " arg "/include")))
+          (setenv "NIX_${infixSalt}_CFLAGS_COMPILE" (concat (getenv "NIX_${infixSalt}_CFLAGS_COMPILE") " -isystem " arg "/include")))
         (when (file-directory-p (concat arg "/lib"))
-          (setenv "NIX_${infixSalt_}LDFLAGS" (concat (getenv "NIX_${infixSalt_}LDFLAGS") " -L" arg "/lib")))
+          (setenv "NIX_${infixSalt}_LDFLAGS" (concat (getenv "NIX_${infixSalt}_LDFLAGS") " -L" arg "/lib")))
         (when (file-directory-p (concat arg "/lib64"))
-          (setenv "NIX_${infixSalt_}LDFLAGS" (concat (getenv "NIX_${infixSalt_}LDFLAGS") " -L" arg "/lib64")))) '(${concatStringsSep " " (map (pkg: "\"${pkg}\"") pkgs)}))
+          (setenv "NIX_${infixSalt}_LDFLAGS" (concat (getenv "NIX_${infixSalt}_LDFLAGS") " -L" arg "/lib64")))) '(${concatStringsSep " " (map (pkg: "\"${pkg}\"") pkgs)}))
     '';
   };
 
@@ -268,7 +240,7 @@ stdenv.mkDerivation {
       # Solaris needs an additional ld wrapper.
       ldPath="${nativePrefix}/bin"
       exec="$ldPath/${prefix}ld"
-      wrap ld-solaris ${preWrap ./ld-solaris-wrapper.sh}
+      wrap ld-solaris ${./ld-solaris-wrapper.sh}
     '')
 
     + ''
@@ -282,7 +254,6 @@ stdenv.mkDerivation {
     '' + (if !useMacosReexportHack then ''
       wrap ${prefix}ld ${./ld-wrapper.sh} ''${ld:-$ldPath/${prefix}ld}
     '' else ''
-      export binPrefix=${prefix}
       ldInner="${prefix}ld-reexport-delegate"
       wrap "$ldInner" ${./macos-sierra-reexport-hack.bash} ''${ld:-$ldPath/${prefix}ld}
       wrap "${prefix}ld" ${./ld-wrapper.sh} "$out/bin/$ldInner"
@@ -290,11 +261,11 @@ stdenv.mkDerivation {
     '') + ''
 
       if [ -e ${binutils_bin}/bin/${prefix}ld.gold ]; then
-        wrap ${prefix}ld.gold ${preWrap ./ld-wrapper.sh} ${binutils_bin}/bin/${prefix}ld.gold
+        wrap ${prefix}ld.gold ${./ld-wrapper.sh} ${binutils_bin}/bin/${prefix}ld.gold
       fi
 
       if [ -e ${binutils_bin}/bin/ld.bfd ]; then
-        wrap ${prefix}ld.bfd ${preWrap ./ld-wrapper.sh} ${binutils_bin}/bin/${prefix}ld.bfd
+        wrap ${prefix}ld.bfd ${./ld-wrapper.sh} ${binutils_bin}/bin/${prefix}ld.bfd
       fi
 
       # We export environment variables pointing to the wrapped nonstandard
@@ -306,49 +277,49 @@ stdenv.mkDerivation {
       export default_cxx_stdlib_compile="${default_cxx_stdlib_compile}"
 
       if [ -e $ccPath/${prefix}gcc ]; then
-        wrap ${prefix}gcc ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}gcc
+        wrap ${prefix}gcc ${./cc-wrapper.sh} $ccPath/${prefix}gcc
         ln -s ${prefix}gcc $out/bin/${prefix}cc
         export named_cc=${prefix}gcc
         export named_cxx=${prefix}g++
       elif [ -e $ccPath/clang ]; then
-        wrap ${prefix}clang ${preWrap ./cc-wrapper.sh} $ccPath/clang
+        wrap ${prefix}clang ${./cc-wrapper.sh} $ccPath/clang
         ln -s ${prefix}clang $out/bin/${prefix}cc
         export named_cc=${prefix}clang
         export named_cxx=${prefix}clang++
       fi
 
       if [ -e $ccPath/${prefix}g++ ]; then
-        wrap ${prefix}g++ ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}g++
+        wrap ${prefix}g++ ${./cc-wrapper.sh} $ccPath/${prefix}g++
         ln -s ${prefix}g++ $out/bin/${prefix}c++
       elif [ -e $ccPath/clang++ ]; then
-        wrap ${prefix}clang++ ${preWrap ./cc-wrapper.sh} $ccPath/clang++
+        wrap ${prefix}clang++ ${./cc-wrapper.sh} $ccPath/clang++
         ln -s ${prefix}clang++ $out/bin/${prefix}c++
       fi
 
       if [ -e $ccPath/cpp ]; then
-        wrap ${prefix}cpp ${preWrap ./cc-wrapper.sh} $ccPath/cpp
+        wrap ${prefix}cpp ${./cc-wrapper.sh} $ccPath/cpp
       fi
     ''
 
     + optionalString cc.langFortran or false ''
-      wrap ${prefix}gfortran ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}gfortran
+      wrap ${prefix}gfortran ${./cc-wrapper.sh} $ccPath/${prefix}gfortran
       ln -sv ${prefix}gfortran $out/bin/${prefix}g77
       ln -sv ${prefix}gfortran $out/bin/${prefix}f77
     ''
 
     + optionalString cc.langJava or false ''
-      wrap ${prefix}gcj ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}gcj
+      wrap ${prefix}gcj ${./cc-wrapper.sh} $ccPath/${prefix}gcj
     ''
 
     + optionalString cc.langGo or false ''
-      wrap ${prefix}gccgo ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}gccgo
+      wrap ${prefix}gccgo ${./cc-wrapper.sh} $ccPath/${prefix}gccgo
     ''
 
     + optionalString cc.langAda or false ''
-      wrap ${prefix}gnatgcc ${preWrap ./cc-wrapper.sh} $ccPath/${prefix}gnatgcc
-      wrap ${prefix}gnatmake ${preWrap ./gnat-wrapper.sh} $ccPath/${prefix}gnatmake
-      wrap ${prefix}gnatbind ${preWrap ./gnat-wrapper.sh} $ccPath/${prefix}gnatbind
-      wrap ${prefix}gnatlink ${preWrap ./gnatlink-wrapper.sh} $ccPath/${prefix}gnatlink
+      wrap ${prefix}gnatgcc ${./cc-wrapper.sh} $ccPath/${prefix}gnatgcc
+      wrap ${prefix}gnatmake ${./gnat-wrapper.sh} $ccPath/${prefix}gnatmake
+      wrap ${prefix}gnatbind ${./gnat-wrapper.sh} $ccPath/${prefix}gnatbind
+      wrap ${prefix}gnatlink ${./gnatlink-wrapper.sh} $ccPath/${prefix}gnatlink
     ''
 
     + optionalString cc.langVhdl or false ''
@@ -356,7 +327,7 @@ stdenv.mkDerivation {
     ''
 
     + ''
-      substituteAll ${preWrap ./setup-hook.sh} $out/nix-support/setup-hook.tmp
+      substituteAll ${./setup-hook.sh} $out/nix-support/setup-hook.tmp
       cat $out/nix-support/setup-hook.tmp >> $out/nix-support/setup-hook
       rm $out/nix-support/setup-hook.tmp
 
@@ -375,9 +346,9 @@ stdenv.mkDerivation {
     ''
 
     + ''
-      substituteAll ${preWrap ./add-flags.sh} $out/nix-support/add-flags.sh
-      substituteAll ${preWrap ./add-hardening.sh} $out/nix-support/add-hardening.sh
-      substituteAll ${preWrap ./utils.sh} $out/nix-support/utils.sh
+      substituteAll ${./add-flags.sh} $out/nix-support/add-flags.sh
+      substituteAll ${./add-hardening.sh} $out/nix-support/add-hardening.sh
+      substituteAll ${./utils.sh} $out/nix-support/utils.sh
     ''
     + extraBuildCommands;
 
diff --git a/pkgs/build-support/cc-wrapper/gnat-wrapper.sh b/pkgs/build-support/cc-wrapper/gnat-wrapper.sh
index dd97a07bd19a..1a09f4841098 100644
--- a/pkgs/build-support/cc-wrapper/gnat-wrapper.sh
+++ b/pkgs/build-support/cc-wrapper/gnat-wrapper.sh
@@ -1,7 +1,10 @@
 #! @shell@
-set -e -o pipefail
+set -eu -o pipefail
 shopt -s nullglob
 
+# N.B. Gnat is not used during bootstrapping, so we don't need to
+# worry about the old bash empty array `set -u` workarounds.
+
 path_backup="$PATH"
 
 # phase separation makes this look useless
@@ -10,12 +13,12 @@ if [ -n "@coreutils_bin@" ]; then
     PATH="@coreutils_bin@/bin"
 fi
 
-if [ -n "$NIX_GNAT_WRAPPER_START_HOOK" ]; then
-    source "$NIX_GNAT_WRAPPER_START_HOOK"
+if [ -z "${NIX_@infixSalt@_GNAT_WRAPPER_FLAGS_SET:-}" ]; then
+    source @out@/nix-support/add-flags.sh
 fi
 
-if [ -z "$NIX_GNAT_WRAPPER_FLAGS_SET" ]; then
-    source @out@/nix-support/add-flags.sh
+if [ -n "$NIX_@infixSalt@_GNAT_WRAPPER_START_HOOK" ]; then
+    source "$NIX_@infixSalt@_GNAT_WRAPPER_START_HOOK"
 fi
 
 source @out@/nix-support/utils.sh
@@ -35,7 +38,7 @@ for i in "$@"; do
         nonFlagArgs=1
     elif [ "$i" = -m32 ]; then
         if [ -e @out@/nix-support/dynamic-linker-m32 ]; then
-            NIX_LDFLAGS+=" -dynamic-linker $(< @out@/nix-support/dynamic-linker-m32)"
+            NIX_@infixSalt@_LDFLAGS+=" -dynamic-linker $(< @out@/nix-support/dynamic-linker-m32)"
         fi
     fi
 done
@@ -52,7 +55,7 @@ fi
 
 # Optionally filter out paths not refering to the store.
 params=("$@")
-if [[ "$NIX_ENFORCE_PURITY" = 1 && -n "$NIX_STORE" ]]; then
+if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "$NIX_STORE" ]]; then
     rest=()
     for p in "${params[@]}"; do
         if [ "${p:0:3}" = -L/ ] && badPath "${p:2}"; then
@@ -72,7 +75,7 @@ fi
 
 
 # Clear march/mtune=native -- they bring impurity.
-if [ "$NIX_ENFORCE_NO_NATIVE" = 1 ]; then
+if [ "$NIX_@infixSalt@_ENFORCE_NO_NATIVE" = 1 ]; then
     rest=()
     for p in "${params[@]}"; do
         if [[ "$p" = -m*=native ]]; then
@@ -86,7 +89,7 @@ fi
 
 
 # Add the flags for the GNAT compiler proper.
-extraAfter=($NIX_GNATFLAGS_COMPILE)
+extraAfter=($NIX_@infixSalt@_GNATFLAGS_COMPILE)
 extraBefore=()
 
 if [ "$(basename "$0")x" = "gnatmakex" ]; then
@@ -95,22 +98,22 @@ fi
 
 #if [ "$dontLink" != 1 ]; then
 #    # Add the flags that should be passed to the linker (and prevent
-#    # `ld-wrapper' from adding NIX_LDFLAGS again).
-#    for i in $NIX_LDFLAGS_BEFORE; do
+#    # `ld-wrapper' from adding NIX_@infixSalt@_LDFLAGS again).
+#    for i in $NIX_@infixSalt@_LDFLAGS_BEFORE; do
 #        extraBefore+=("-largs" "$i")
 #    done
-#    for i in $NIX_LDFLAGS; do
+#    for i in $NIX_@infixSalt@_LDFLAGS; do
 #        if [ "${i:0:3}" = -L/ ]; then
 #            extraAfter+=("$i")
 #        else
 #            extraAfter+=("-largs" "$i")
 #        fi
 #    done
-#    export NIX_LDFLAGS_SET=1
+#    export NIX_@infixSalt@_LDFLAGS_SET=1
 #fi
 
 # Optionally print debug info.
-if [ -n "$NIX_DEBUG" ]; then
+if [ -n "${NIX_DEBUG:-}" ]; then
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2
@@ -119,8 +122,8 @@ if [ -n "$NIX_DEBUG" ]; then
     printf "  %q\n" "${extraAfter[@]}" >&2
 fi
 
-if [ -n "$NIX_GNAT_WRAPPER_EXEC_HOOK" ]; then
-    source "$NIX_GNAT_WRAPPER_EXEC_HOOK"
+if [ -n "$NIX_@infixSalt@_GNAT_WRAPPER_EXEC_HOOK" ]; then
+    source "$NIX_@infixSalt@_GNAT_WRAPPER_EXEC_HOOK"
 fi
 
 PATH="$path_backup"
diff --git a/pkgs/build-support/cc-wrapper/gnatlink-wrapper.sh b/pkgs/build-support/cc-wrapper/gnatlink-wrapper.sh
index 3c1a805c3fa3..ee973d3270f9 100644
--- a/pkgs/build-support/cc-wrapper/gnatlink-wrapper.sh
+++ b/pkgs/build-support/cc-wrapper/gnatlink-wrapper.sh
@@ -1,27 +1,30 @@
 #! @shell@
-set -e -o pipefail
+set -eu -o pipefail
 shopt -s nullglob
 
+# N.B. Gnat is not used during bootstrapping, so we don't need to
+# worry about the old bash empty array `set -u` workarounds.
+
 # Add the flags for the GNAT compiler proper.
 extraAfter=("--GCC=@out@/bin/gcc")
 extraBefore=()
 
 ## Add the flags that should be passed to the linker (and prevent
-## `ld-wrapper' from adding NIX_LDFLAGS again).
-#for i in $NIX_LDFLAGS_BEFORE; do
+## `ld-wrapper' from adding NIX_@infixSalt@_LDFLAGS again).
+#for i in $NIX_@infixSalt@_LDFLAGS_BEFORE; do
 #    extraBefore+=("-largs" "$i")
 #done
-#for i in $NIX_LDFLAGS; do
+#for i in $NIX_@infixSalt@_LDFLAGS; do
 #    if [ "${i:0:3}" = -L/ ]; then
 #        extraAfter+=("$i")
 #    else
 #        extraAfter+=("-largs" "$i")
 #    fi
 #done
-#export NIX_LDFLAGS_SET=1
+#export NIX_@infixSalt@_LDFLAGS_SET=1
 
 # Optionally print debug info.
-if [ -n "$NIX_DEBUG" ]; then
+if [ -n "${NIX_DEBUG:-}" ]; then
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2
@@ -30,8 +33,8 @@ if [ -n "$NIX_DEBUG" ]; then
     printf "  %q\n" "${extraAfter[@]}" >&2
 fi
 
-if [ -n "$NIX_GNAT_WRAPPER_EXEC_HOOK" ]; then
-    source "$NIX_GNAT_WRAPPER_EXEC_HOOK"
+if [ -n "$NIX_@infixSalt@_GNAT_WRAPPER_EXEC_HOOK" ]; then
+    source "$NIX_@infixSalt@_GNAT_WRAPPER_EXEC_HOOK"
 fi
 
 exec @prog@ "${extraBefore[@]}" "$@" "${extraAfter[@]}"
diff --git a/pkgs/build-support/cc-wrapper/ld-wrapper.sh b/pkgs/build-support/cc-wrapper/ld-wrapper.sh
index 6ee66b0e3f2b..d0a1d5a0ddb7 100644
--- a/pkgs/build-support/cc-wrapper/ld-wrapper.sh
+++ b/pkgs/build-support/cc-wrapper/ld-wrapper.sh
@@ -1,5 +1,5 @@
 #! @shell@
-set -e -o pipefail
+set -eu -o pipefail
 shopt -s nullglob
 
 path_backup="$PATH"
@@ -10,12 +10,12 @@ if [ -n "@coreutils_bin@" ]; then
     PATH="@coreutils_bin@/bin"
 fi
 
-if [ -n "$NIX_LD_WRAPPER_START_HOOK" ]; then
-    source "$NIX_LD_WRAPPER_START_HOOK"
+if [ -z "${NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET:-}" ]; then
+    source @out@/nix-support/add-flags.sh
 fi
 
-if [ -z "$NIX_CC_WRAPPER_FLAGS_SET" ]; then
-    source @out@/nix-support/add-flags.sh
+if [ -n "$NIX_LD_WRAPPER_@infixSalt@_START_HOOK" ]; then
+    source "$NIX_LD_WRAPPER_@infixSalt@_START_HOOK"
 fi
 
 source @out@/nix-support/utils.sh
@@ -23,14 +23,14 @@ source @out@/nix-support/utils.sh
 
 # Optionally filter out paths not refering to the store.
 expandResponseParams "$@"
-if [[ "$NIX_ENFORCE_PURITY" = 1 && -n "$NIX_STORE"
-        && ( -z "$NIX_IGNORE_LD_THROUGH_GCC" || -z "$NIX_LDFLAGS_SET" ) ]]; then
+if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "${NIX_STORE:-}"
+        && ( -z "$NIX_@infixSalt@_IGNORE_LD_THROUGH_GCC" || -z "${NIX_@infixSalt@_LDFLAGS_SET:-}" ) ]]; then
     rest=()
     nParams=${#params[@]}
     declare -i n=0
     while [ "$n" -lt "$nParams" ]; do
         p=${params[n]}
-        p2=${params[n+1]}
+        p2=${params[n+1]:-} # handle `p` being last one
         if [ "${p:0:3}" = -L/ ] && badPath "${p:2}"; then
             skip "${p:2}"
         elif [ "$p" = -L ] && badPath "$p2"; then
@@ -59,21 +59,25 @@ source @out@/nix-support/add-hardening.sh
 extraAfter=("${hardeningLDFlags[@]}")
 extraBefore=()
 
-if [ -z "$NIX_LDFLAGS_SET" ]; then
-    extraAfter+=($NIX_LDFLAGS)
-    extraBefore+=($NIX_LDFLAGS_BEFORE)
+if [ -z "${NIX_@infixSalt@_LDFLAGS_SET:-}" ]; then
+    extraAfter+=($NIX_@infixSalt@_LDFLAGS)
+    extraBefore+=($NIX_@infixSalt@_LDFLAGS_BEFORE)
 fi
 
-extraAfter+=($NIX_LDFLAGS_AFTER $NIX_LDFLAGS_HARDEN)
+extraAfter+=($NIX_@infixSalt@_LDFLAGS_AFTER $NIX_@infixSalt@_LDFLAGS_HARDEN)
 
 declare -a libDirs
 declare -A libs
 relocatable=
 
 # Find all -L... switches for rpath, and relocatable flags for build id.
-if [ "$NIX_DONT_SET_RPATH" != 1 ] || [ "$NIX_SET_BUILD_ID" = 1 ]; then
+if [ "$NIX_@infixSalt@_DONT_SET_RPATH" != 1 ] || [ "$NIX_@infixSalt@_SET_BUILD_ID" = 1 ]; then
     prev=
+    # Old bash thinks empty arrays are undefined, ugh, so temporarily disable
+    # `set -u`.
+    set +u
     for p in "${extraBefore[@]}" "${params[@]}" "${extraAfter[@]}"; do
+        set -u
         case "$prev" in
             -L)
                 libDirs+=("$p")
@@ -92,7 +96,7 @@ if [ "$NIX_DONT_SET_RPATH" != 1 ] || [ "$NIX_SET_BUILD_ID" = 1 ]; then
                     -l?*)
                         libs["lib${p:2}.so"]=1
                         ;;
-                    "$NIX_STORE"/*.so | "$NIX_STORE"/*.so.*)
+                    "${NIX_STORE:-}"/*.so | "${NIX_STORE:-}"/*.so.*)
                         # This is a direct reference to a shared library.
                         libDirs+=("${p%/*}")
                         libs["${p##*/}"]=1
@@ -108,7 +112,7 @@ fi
 
 
 # Add all used dynamic libraries to the rpath.
-if [ "$NIX_DONT_SET_RPATH" != 1 ]; then
+if [ "$NIX_@infixSalt@_DONT_SET_RPATH" != 1 ]; then
     # For each directory in the library search path (-L...),
     # see if it contains a dynamic library used by a -l... flag.  If
     # so, add the directory to the rpath.
@@ -119,20 +123,23 @@ if [ "$NIX_DONT_SET_RPATH" != 1 ]; then
         if [[ "$dir" =~ [/.][/.] ]] && dir2=$(readlink -f "$dir"); then
             dir="$dir2"
         fi
-        if [ "${rpaths[$dir]}" ] || [[ "$dir" != "$NIX_STORE"/* ]]; then
+        if [ -n "${rpaths[$dir]:-}" ] || [[ "$dir" != "${NIX_STORE:-}"/* ]]; then
             # If the path is not in the store, don't add it to the rpath.
             # This typically happens for libraries in /tmp that are later
             # copied to $out/lib.  If not, we're screwed.
             continue
         fi
-        for path in "$dir"/lib*.so; do
+        for path in "$dir"/*; do
             file="${path##*/}"
-            if [ "${libs[$file]}" ]; then
-                libs["$file"]=
-                if [ ! "${rpaths[$dir]}" ]; then
-                    rpaths["$dir"]=1
-                    extraAfter+=(-rpath "$dir")
-                fi
+            if [ "${libs[$file]:-}" ]; then
+                # This library may have been provided by a previous directory,
+                # but if that library file is inside an output of the current
+                # derivation, it can be deleted after this compilation and
+                # should be found in a later directory, so we add all
+                # directories that contain any of the libraries to rpath.
+                rpaths["$dir"]=1
+                extraAfter+=(-rpath "$dir")
+                break
             fi
         done
     done
@@ -141,24 +148,27 @@ fi
 
 # Only add --build-id if this is a final link. FIXME: should build gcc
 # with --enable-linker-build-id instead?
-if [ "$NIX_SET_BUILD_ID" = 1 ] && [ ! "$relocatable" ]; then
+if [ "$NIX_@infixSalt@_SET_BUILD_ID" = 1 ] && [ ! "$relocatable" ]; then
     extraAfter+=(--build-id)
 fi
 
 
 # Optionally print debug info.
-if [ -n "$NIX_DEBUG" ]; then
+if [ -n "${NIX_DEBUG:-}" ]; then
+    set +u # Old bash workaround, see above.
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2
     printf "  %q\n" "${params[@]}" >&2
     echo "extra flags after to @prog@:" >&2
     printf "  %q\n" "${extraAfter[@]}" >&2
+    set -u
 fi
 
-if [ -n "$NIX_LD_WRAPPER_EXEC_HOOK" ]; then
-    source "$NIX_LD_WRAPPER_EXEC_HOOK"
+if [ -n "$NIX_LD_WRAPPER_@infixSalt@_EXEC_HOOK" ]; then
+    source "$NIX_LD_WRAPPER_@infixSalt@_EXEC_HOOK"
 fi
 
 PATH="$path_backup"
+set +u # Old bash workaround, see above.
 exec @prog@ "${extraBefore[@]}" "${params[@]}" "${extraAfter[@]}"
diff --git a/pkgs/build-support/cc-wrapper/setup-hook.sh b/pkgs/build-support/cc-wrapper/setup-hook.sh
index 2bf507ce8dff..c6abd6281d26 100644
--- a/pkgs/build-support/cc-wrapper/setup-hook.sh
+++ b/pkgs/build-support/cc-wrapper/setup-hook.sh
@@ -1,22 +1,112 @@
-addCVars () {
+# CC Wrapper hygiene
+#
+# For at least cross compilation, we need to depend on multiple cc-wrappers at
+# once---specifically up to one per sort of dependency. This follows from having
+# different tools targeting different platforms, and different flags for those
+# tools. For example:
+#
+#   # Flags for compiling (whether or not linking) C code for the...
+#   NIX_BUILD_CFLAGS_COMPILE  # ...build platform
+#   NIX_CFLAGS_COMPILE        # ...host platform
+#   NIX_TARGET_CFLAGS_COMPILE # ...target platform
+#
+# Notice that these platforms are the 3 *relative* to the package using
+# cc-wrapper, not absolute like `x86_64-pc-linux-gnu`.
+#
+# The simplest solution would be to have separate cc-wrappers per (3 intended
+# use-cases * n absolute concrete platforms). For the use-case axis, we would
+# @-splice in 'BUILD_' '' 'TARGET_' to use the write environment variables when
+# building the cc-wrapper, and likewise prefix the binaries' names so they didn't
+# clobber each other on the PATH. But the need for 3x cc-wrappers, along with
+# non-standard name prefixes, is annoying and liable to break packages' build
+# systems.
+#
+# Instead, we opt to have just one cc-wrapper per absolute platform. Matching
+# convention, the binaries' names can just be prefixed with their target
+# platform. On the other hand, that means packages will depend on not just
+# multiple cc-wrappers, but the exact same cc-wrapper derivation multiple ways.
+# That means the exact same cc-wrapper derivation must be able to avoid
+# conflicting with itself, despite the fact that `setup-hook.sh`, the `addCvars`
+# function, and `add-flags.sh` are all communicating with each other with
+# environment variables. Yuck.
+#
+# The basic strategy is:
+#
+#  - Everyone exclusively *adds information* to relative-platform-specific
+#    environment variables, like `NIX_TARGET_CFLAGS_COMPILE`, to communicate
+#    with the wrapped binaries.
+#
+#  - The wrapped binaries will exclusively *read* cc-wrapper-derivation-specific
+#    environment variables distinguished with with `infixSalt`, like
+#    `NIX_@infixSalt@_CFLAGS_COMPILE`.
+#
+#  - `add-flags`, beyond its old task of reading extra flags stuck inside the
+#    cc-wrapper derivation, will convert the relative-platform-specific
+#    variables to cc-wrapper-derivation-specific variables. This conversion is
+#    the only time all but one of the cc-wrapper-derivation-specific variables
+#    are set.
+#
+# This ensures the flow of information is exclusive from
+# relative-platform-specific variables to cc-wrapper-derivation-specific
+# variables. This allows us to support the general case of a many--many relation
+# between relative platforms and cc-wrapper derivations.
+#
+# For more details, read the individual files where the mechanisms used to
+# accomplish this will be individually documented.
+
+
+# It's fine that any other cc-wrapper will redefine this. Bash functions close
+# over no state, and there's no @-substitutions within, so any redefined
+# function is guaranteed to be exactly the same.
+ccWrapper_addCVars () {
+    # The `depOffset` describes how the platforms of the dependencies are slid
+    # relative to the depending package. It is brought into scope of the
+    # environment hook defined as the role of the dependency being applied.
+    case $depOffset in
+        -1) local role='BUILD_' ;;
+        0)  local role='' ;;
+        1)  local role='TARGET_' ;;
+        *)  echo "cc-wrapper: Error: Cannot be used with $depOffset-offset deps, " >2;
+            return 1 ;;
+    esac
+
     if [[ -d "$1/include" ]]; then
-        export NIX_CFLAGS_COMPILE+=" ${ccIncludeFlag:--isystem} $1/include"
+        export NIX_${role}CFLAGS_COMPILE+=" ${ccIncludeFlag:--isystem} $1/include"
     fi
 
     if [[ -d "$1/lib64" && ! -L "$1/lib64" ]]; then
-        export NIX_LDFLAGS+=" -L$1/lib64"
+        export NIX_${role}LDFLAGS+=" -L$1/lib64"
     fi
 
     if [[ -d "$1/lib" ]]; then
-        export NIX_LDFLAGS+=" -L$1/lib"
+        export NIX_${role}LDFLAGS+=" -L$1/lib"
     fi
 
     if [[ -d "$1/Library/Frameworks" ]]; then
-        export NIX_CFLAGS_COMPILE+=" -F$1/Library/Frameworks"
+        export NIX_${role}CFLAGS_COMPILE+=" -F$1/Library/Frameworks"
     fi
 }
 
-envHooks+=(addCVars)
+# Since the same cc-wrapper derivation can be depend on in multiple ways, we
+# need to accumulate *each* role (i.e. target platform relative the depending
+# derivation) in which the cc-wrapper derivation is used.
+# `NIX_CC_WRAPPER_@infixSalt@_TARGET_*` tracks this (needs to be an exported env
+# var so can't use fancier data structures).
+#
+# We also need to worry about what role is being added on *this* invocation of
+# setup-hook, which `role` tracks.
+if [ -n "${crossConfig:-}" ]; then
+    export NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD=1
+    role="BUILD_"
+else
+    export NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST=1
+    role=""
+fi
+
+# Eventually the exact sort of env-hook we create will depend on the role. This
+# is because based on what relative platform we are targeting, we use different
+# dependencies.
+envHooks+=(ccWrapper_addCVars)
 
 # Note 1: these come *after* $out in the PATH (see setup.sh).
 # Note 2: phase separation makes this look useless to shellcheck.
@@ -41,16 +131,12 @@ if [ -n "@coreutils_bin@" ]; then
     addToSearchPath _PATH @coreutils_bin@/bin
 fi
 
-if [ -z "${crossConfig:-}" ]; then
-    ENV_PREFIX=""
-else
-    ENV_PREFIX="BUILD_"
-fi
+# Export tool environment variables so various build systems use the right ones.
 
-export NIX_${ENV_PREFIX}CC=@out@
+export NIX_${role}CC=@out@
 
-export ${ENV_PREFIX}CC=@named_cc@
-export ${ENV_PREFIX}CXX=@named_cxx@
+export ${role}CC=@named_cc@
+export ${role}CXX=@named_cxx@
 
 for CMD in \
     cpp \
@@ -59,9 +145,9 @@ do
     if
         PATH=$_PATH type -p "@binPrefix@$CMD" > /dev/null
     then
-        export "${ENV_PREFIX}$(echo "$CMD" | tr "[:lower:]" "[:upper:]")=@binPrefix@${CMD}";
+        export "${role}$(echo "$CMD" | tr "[:lower:]" "[:upper:]")=@binPrefix@${CMD}";
     fi
 done
 
-# No local scope available for sourced files
-unset ENV_PREFIX
+# No local scope in sourced file
+unset role
diff --git a/pkgs/build-support/cc-wrapper/utils.sh b/pkgs/build-support/cc-wrapper/utils.sh
index 267044b2c4f3..5a70c2d9ccf3 100644
--- a/pkgs/build-support/cc-wrapper/utils.sh
+++ b/pkgs/build-support/cc-wrapper/utils.sh
@@ -1,5 +1,5 @@
 skip () {
-    if [ -n "$NIX_DEBUG" ]; then
+    if [ -n "${NIX_DEBUG:-}" ]; then
         echo "skipping impure path $1" >&2
     fi
 }
diff --git a/pkgs/build-support/setup-hooks/die.sh b/pkgs/build-support/setup-hooks/die.sh
new file mode 100644
index 000000000000..0db41e030f4c
--- /dev/null
+++ b/pkgs/build-support/setup-hooks/die.sh
@@ -0,0 +1,21 @@
+# Exit with backtrace and error message
+#
+# Usage: die "Error message"
+die() {
+    # Let us be a little sloppy with errors, because otherwise the final
+    # invocation of `caller` below will cause the script to exit.
+    set +e
+
+    # Print our error message
+    printf "\nBuilder called die: %b\n" "$*"
+    printf "Backtrace:\n"
+
+    # Print a backtrace.
+    local frame=0
+    while caller $frame; do
+        ((frame++));
+    done
+    printf "\n"
+
+    exit 1
+}
diff --git a/pkgs/build-support/setup-hooks/make-wrapper.sh b/pkgs/build-support/setup-hooks/make-wrapper.sh
index eebde886a884..cde28fbbcaf1 100644
--- a/pkgs/build-support/setup-hooks/make-wrapper.sh
+++ b/pkgs/build-support/setup-hooks/make-wrapper.sh
@@ -1,3 +1,12 @@
+# Assert that FILE exists and is executable
+#
+# assertExecutable FILE
+assertExecutable() {
+    local file="$1"
+    [[ -f "${file}" && -x "${file}" ]] || \
+        die "Cannot wrap ${file} because it is not an executable file"
+}
+
 # construct an executable file that wraps the actual executable
 # makeWrapper EXECUTABLE ARGS
 
@@ -24,6 +33,8 @@ makeWrapper() {
     local params varName value command separator n fileNames
     local argv0 flagsBefore flags
 
+    assertExecutable "${original}"
+
     mkdir -p "$(dirname "$wrapper")"
 
     echo "#! $SHELL -e" > "$wrapper"
@@ -32,26 +43,20 @@ makeWrapper() {
     for ((n = 2; n < ${#params[*]}; n += 1)); do
         p="${params[$n]}"
 
-        if test "$p" = "--set"; then
+        if [[ "$p" == "--set" ]]; then
             varName="${params[$((n + 1))]}"
             value="${params[$((n + 2))]}"
             n=$((n + 2))
             echo "export $varName=\"$value\"" >> "$wrapper"
-        fi
-
-        if test "$p" = "--unset"; then
+        elif [[ "$p" == "--unset" ]]; then
             varName="${params[$((n + 1))]}"
             n=$((n + 1))
             echo "unset $varName" >> "$wrapper"
-        fi
-
-        if test "$p" = "--run"; then
+        elif [[ "$p" == "--run" ]]; then
             command="${params[$((n + 1))]}"
             n=$((n + 1))
             echo "$command" >> "$wrapper"
-        fi
-
-        if test "$p" = "--suffix" -o "$p" = "--prefix"; then
+        elif [[ ("$p" == "--suffix") || ("$p" == "--prefix") ]]; then
             varName="${params[$((n + 1))]}"
             separator="${params[$((n + 2))]}"
             value="${params[$((n + 3))]}"
@@ -63,9 +68,7 @@ makeWrapper() {
                     echo "export $varName=$value\${$varName:+$separator}\$$varName" >> "$wrapper"
                 fi
             fi
-        fi
-
-        if test "$p" = "--suffix-each"; then
+        elif [[ "$p" == "--suffix-each" ]]; then
             varName="${params[$((n + 1))]}"
             separator="${params[$((n + 2))]}"
             values="${params[$((n + 3))]}"
@@ -73,9 +76,7 @@ makeWrapper() {
             for value in $values; do
                 echo "export $varName=\$$varName\${$varName:+$separator}$value" >> "$wrapper"
             done
-        fi
-
-        if test "$p" = "--suffix-contents" -o "$p" = "--prefix-contents"; then
+        elif [[ ("$p" == "--suffix-contents") || ("$p" == "--prefix-contents") ]]; then
             varName="${params[$((n + 1))]}"
             separator="${params[$((n + 2))]}"
             fileNames="${params[$((n + 3))]}"
@@ -87,17 +88,15 @@ makeWrapper() {
                     echo "export $varName=$(cat "$fileName")\${$varName:+$separator}\$$varName" >> "$wrapper"
                 fi
             done
-        fi
-
-        if test "$p" = "--add-flags"; then
+        elif [[ "$p" == "--add-flags" ]]; then
             flags="${params[$((n + 1))]}"
             n=$((n + 1))
             flagsBefore="$flagsBefore $flags"
-        fi
-
-        if test "$p" = "--argv0"; then
+        elif [[ "$p" == "--argv0" ]]; then
             argv0="${params[$((n + 1))]}"
             n=$((n + 1))
+        else
+            die "makeWrapper doesn't understand the arg $p"
         fi
     done
 
@@ -131,6 +130,9 @@ filterExisting() {
 wrapProgram() {
     local prog="$1"
     local hidden
+
+    assertExecutable "${prog}"
+
     hidden="$(dirname "$prog")/.$(basename "$prog")"-wrapped
     while [ -e "$hidden" ]; do
       hidden="${hidden}_"
@@ -138,5 +140,5 @@ wrapProgram() {
     mv "$prog" "$hidden"
     # Silence warning about unexpanded $0:
     # shellcheck disable=SC2016
-    makeWrapper "$hidden" "$prog" --argv0 '$0' "$@"
+    makeWrapper "$hidden" "$prog" --argv0 '$0' "${@:2}"
 }
diff --git a/pkgs/desktops/gnome-3/3.22/core/evolution-data-server/default.nix b/pkgs/desktops/gnome-3/3.22/core/evolution-data-server/default.nix
index a8c3f724b850..c2038ecdce60 100644
--- a/pkgs/desktops/gnome-3/3.22/core/evolution-data-server/default.nix
+++ b/pkgs/desktops/gnome-3/3.22/core/evolution-data-server/default.nix
@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   preFixup = ''
-    for f in "$out/libexec/"*; do
+    for f in $(find $out/libexec/ -type f -executable); do
       wrapProgram "$f" \
         --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH" \
         --prefix GIO_EXTRA_MODULES : "${stdenv.lib.getLib dconf}/lib/gio/modules"
diff --git a/pkgs/development/interpreters/python/wrapper.nix b/pkgs/development/interpreters/python/wrapper.nix
index f95e51c82ee7..9f355ddefda7 100644
--- a/pkgs/development/interpreters/python/wrapper.nix
+++ b/pkgs/development/interpreters/python/wrapper.nix
@@ -28,7 +28,9 @@ let
           for prg in *; do
             if [ -f "$prg" ]; then
               rm -f "$out/bin/$prg"
-              makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set PYTHONHOME "$out" --set PYTHONNOUSERSITE "true"
+              if [ -x "$prg" ]; then
+                makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set PYTHONHOME "$out" --set PYTHONNOUSERSITE "true"
+              fi
             fi
           done
         fi
diff --git a/pkgs/development/libraries/serf/default.nix b/pkgs/development/libraries/serf/default.nix
index c10a355dee02..001199cd8212 100644
--- a/pkgs/development/libraries/serf/default.nix
+++ b/pkgs/development/libraries/serf/default.nix
@@ -1,4 +1,5 @@
-{ stdenv, fetchurl, apr, scons, openssl, aprutil, zlib, kerberos, pkgconfig, gnused }:
+{ stdenv, fetchurl, apr, scons, openssl, aprutil, zlib, kerberos
+, pkgconfig, gnused, expat, openldap, libiconv }:
 
 stdenv.mkDerivation rec {
   name = "serf-1.3.9";
@@ -8,18 +9,22 @@ stdenv.mkDerivation rec {
     sha256 = "1k47gbgpp52049andr28y28nbwh9m36bbb0g8p0aka3pqlhjv72l";
   };
 
-  buildInputs = [ apr scons openssl aprutil zlib ]
-    ++ stdenv.lib.optional (!stdenv.isCygwin) kerberos
-    ++ [ pkgconfig ];
+  nativeBuildInputs = [ pkgconfig ];
+  buildInputs = [ apr scons openssl aprutil zlib libiconv ]
+    ++ stdenv.lib.optional (!stdenv.isCygwin) kerberos;
 
-  configurePhase = ''
-    ${gnused}/bin/sed -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"PATH":os.environ["PATH"]})' -i SConstruct
-    ${gnused}/bin/sed -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"NIX_CFLAGS_COMPILE":os.environ["NIX_CFLAGS_COMPILE"]})' -i SConstruct
-    ${gnused}/bin/sed -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"NIX_LDFLAGS":os.environ["NIX_LDFLAGS"]})' -i SConstruct
+  postPatch = ''
+    sed -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"PATH":os.environ["PATH"]})' \
+        -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"NIX_CFLAGS_COMPILE":os.environ["NIX_CFLAGS_COMPILE"]})' \
+        -e '/^env[.]Append(BUILDERS/ienv.Append(ENV={"NIX_LDFLAGS":os.environ["NIX_LDFLAGS"]})' \
+        -e 's,$OPENSSL/lib,${openssl.out}/lib,' \
+        -e 's,$OPENSSL/include,${openssl.dev}/include,' \
+      -i SConstruct
   '';
 
   buildPhase = ''
-    scons PREFIX="$out" OPENSSL="${openssl.dev}" ZLIB="${zlib.dev}" APR="$(echo "${apr.dev}"/bin/*-config)" \
+    scons PREFIX="$out" OPENSSL="${openssl}" ZLIB="${zlib}" APR="$(echo "${apr.dev}"/bin/*-config)" CFLAGS="-I${zlib.dev}/include" \
+      LINKFLAGS="-L${zlib.out}/lib -L${expat}/lib -L${openldap}/lib -L${libiconv}/lib" \
         APU="$(echo "${aprutil.dev}"/bin/*-config)" CC="${
           if stdenv.cc.isClang then "clang" else "${stdenv.cc}/bin/gcc"
         }" ${
diff --git a/pkgs/os-specific/linux/bcc/default.nix b/pkgs/os-specific/linux/bcc/default.nix
index 38f57e7663eb..24686e73e23a 100644
--- a/pkgs/os-specific/linux/bcc/default.nix
+++ b/pkgs/os-specific/linux/bcc/default.nix
@@ -25,11 +25,13 @@ stdenv.mkDerivation rec {
     mv $out/share/bcc/man $out/share/
 
     for f in $out/share/bcc/tools\/*; do
-      ln -s $f $out/bin/$(basename $f)
-      wrapProgram $f \
-        --prefix LD_LIBRARY_PATH : $out/lib \
-        --prefix PYTHONPATH : $out/lib/python2.7/site-packages \
-        --prefix PYTHONPATH : :${pythonPackages.netaddr}/lib/${python.libPrefix}/site-packages
+      if [ -x $f ]; then
+        ln -s $f $out/bin/$(basename $f)
+        wrapProgram $f \
+          --prefix LD_LIBRARY_PATH : $out/lib \
+          --prefix PYTHONPATH : $out/lib/python2.7/site-packages \
+          --prefix PYTHONPATH : ${pythonPackages.netaddr}/lib/${python.libPrefix}/site-packages
+      fi
     done
   '';
 
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index dc3369f6611c..81ed1c635e17 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -336,8 +336,20 @@ fi
 
 # Set the relevant environment variables to point to the build inputs
 # found above.
+#
+# These `depOffset`s tell the env hook what sort of dependency
+# (ignoring propagatedness) is being passed to the env hook. In a real
+# language, we'd append a closure with this information to the
+# relevant env hook array, but bash doesn't have closures, so it's
+# easier to just pass this in.
+
 _addToNativeEnv() {
     local pkg="$1"
+    if [[ -n "${crossConfig:-}" ]]; then
+        local -i depOffset=-1
+    else
+        local -i depOffset=0
+    fi
 
     # Run the package-specific hooks set by the setup-hook scripts.
     runHook envHook "$pkg"
@@ -349,6 +361,7 @@ done
 
 _addToCrossEnv() {
     local pkg="$1"
+    local -i depOffset=0
 
     # Run the package-specific hooks set by the setup-hook scripts.
     runHook crossEnvHook "$pkg"
diff --git a/pkgs/tools/archivers/unzip/default.nix b/pkgs/tools/archivers/unzip/default.nix
index a35e473ec366..7c4bb988b629 100644
--- a/pkgs/tools/archivers/unzip/default.nix
+++ b/pkgs/tools/archivers/unzip/default.nix
@@ -37,7 +37,7 @@ stdenv.mkDerivation {
 
   makefile = "unix/Makefile";
 
-  ${"NIX_${stdenv.cc.infixSalt_}LDFLAGS"} = [ "-lbz2" ] ++ stdenv.lib.optional enableNLS "-lnatspec";
+  NIX_LDFLAGS = [ "-lbz2" ] ++ stdenv.lib.optional enableNLS "-lnatspec";
 
   buildFlags = "generic D_USE_BZ2=-DUSE_BZIP2 L_BZ2=-lbz2";
 
diff --git a/pkgs/tools/misc/screenfetch/default.nix b/pkgs/tools/misc/screenfetch/default.nix
index c138261f9a33..a781ff910270 100644
--- a/pkgs/tools/misc/screenfetch/default.nix
+++ b/pkgs/tools/misc/screenfetch/default.nix
@@ -21,17 +21,10 @@ stdenv.mkDerivation {
     # Fix all of the depedencies of screenfetch
     patchShebangs $out/bin/screenfetch
     wrapProgram "$out/bin/screenfetch" \
-      --set PATH : "" \
-      --prefix PATH : "${coreutils}/bin" \
-      --prefix PATH : "${gawk}/bin" \
-      --prefix PATH : "${procps}/bin" \
-      --prefix PATH : "${gnused}/bin" \
-      --prefix PATH : "${findutils}/bin" \
-      --prefix PATH : "${xdpyinfo}/bin" \
-      --prefix PATH : "${xprop}/bin" \
-      --prefix PATH : "${gnugrep}/bin" \
-      --prefix PATH : "${ncurses}/bin" \
-      --prefix PATH : "${bc}/bin"
+      --set PATH ${stdenv.lib.makeBinPath [
+        coreutils gawk procps gnused findutils xdpyinfo
+        xprop gnugrep ncurses bc
+      ]}
   '';
 
   meta = {
diff --git a/pkgs/tools/package-management/nix-prefetch-scripts/default.nix b/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
index f37940c65c1e..291b1a7c6002 100644
--- a/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
+++ b/pkgs/tools/package-management/nix-prefetch-scripts/default.nix
@@ -19,7 +19,7 @@ let mkPrefetchScript = tool: src: deps:
       done
       wrapArgs="$wrapArgs --prefix PATH : ${gnused}/bin"
       wrapArgs="$wrapArgs --prefix PATH : ${nix.out}/bin" # For nix-hash
-      wrapArgs="$wrapArgs --set HOME : /homeless-shelter"
+      wrapArgs="$wrapArgs --set HOME /homeless-shelter"
       wrapProgram $out/bin/$name $wrapArgs
     '';
 
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 2b7fa8ef239a..a31aefbab694 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -100,6 +100,8 @@ with pkgs;
 
   diffPlugins = (callPackage ../build-support/plugins.nix {}).diffPlugins;
 
+  dieHook = makeSetupHook {} ../build-support/setup-hooks/die.sh;
+
   dockerTools = callPackage ../build-support/docker { };
 
   docker_compose = pythonPackages.docker_compose;
@@ -287,7 +289,8 @@ with pkgs;
       inherit contents compressor prepend;
     };
 
-  makeWrapper = makeSetupHook { } ../build-support/setup-hooks/make-wrapper.sh;
+  makeWrapper = makeSetupHook { deps = [ dieHook ]; }
+                              ../build-support/setup-hooks/make-wrapper.sh;
 
   makeModulesClosure = { kernel, rootModules, allowMissing ? false }:
     callPackage ../build-support/kernel/modules-closure.nix {