go-modules/packages: Run unit tests under subdirs

Bug:
Due to the way `buildGoDir` function was repurposed to also run `go
test`, if `checkFlags` was defined, `go test` was ran only at the top
level directory. Only the first element of `checkFlags` array would get
passed to the `go test` command as arguments.

Fix:
Now the first parameter to `buildGoDir` is handled as the command.  If
the command is "test" `checkFlags` get passed as arguments along with
other build flags like ldflags, tags, etc.

Readability:
- Iteratively build a flag array in `buildGoDir` instead of single long
  variable expansion command line.
- Bash style: Single line local assignment of positional parameters.

pkgs/development/go-modules/generic/default.nix

@@ -180,12 +180,22 @@ let
       exclude+='\)'
 
       buildGoDir() {
-        local d; local cmd;
-        cmd="$1"
-        d="$2"
+        local cmd="$1" dir="$2"
+
         . $TMPDIR/buildFlagsArray
+
+        declare -a flags
+        flags+=($buildFlags "''${buildFlagsArray[@]}")
+        flags+=(''${tags:+-tags=${lib.concatStringsSep "," tags}})
+        flags+=(''${ldflags:+-ldflags="$ldflags"})
+        flags+=("-v" "-p" "$NIX_BUILD_CORES")
+
+        if [ "$cmd" = "test" ]; then
+          flags+=($checkFlags)
+        fi
+
         local OUT
-        if ! OUT="$(go $cmd $buildFlags "''${buildFlagsArray[@]}" ''${tags:+-tags=${lib.concatStringsSep "," tags}} ''${ldflags:+-ldflags="$ldflags"} -v -p $NIX_BUILD_CORES $d 2>&1)"; then
+        if ! OUT="$(go $cmd "''${flags[@]}" $dir 2>&1)"; then
           if ! echo "$OUT" | grep -qE '(no( buildable| non-test)?|build constraints exclude all) Go (source )?files'; then
             echo "$OUT" >&2
             return 1
@@ -243,7 +253,7 @@ let
       runHook preCheck
 
       for pkg in $(getGoDirs test); do
-        buildGoDir test $checkFlags "$pkg"
+        buildGoDir test "$pkg"
       done
 
       runHook postCheck

pkgs/development/go-packages/generic/default.nix

@@ -160,12 +160,22 @@ let
       exclude+='\)'
 
       buildGoDir() {
-        local d; local cmd;
-        cmd="$1"
-        d="$2"
+        local cmd="$1" dir="$2"
+
         . $TMPDIR/buildFlagsArray
+
+        declare -a flags
+        flags+=($buildFlags "''${buildFlagsArray[@]}")
+        flags+=(''${tags:+-tags=${lib.concatStringsSep "," tags}})
+        flags+=(''${ldflags:+-ldflags="$ldflags"})
+        flags+=("-v" "-p" "$NIX_BUILD_CORES")
+
+        if [ "$cmd" = "test" ]; then
+          flags+=($checkFlags)
+        fi
+
         local OUT
-        if ! OUT="$(go $cmd $buildFlags "''${buildFlagsArray[@]}" ''${tags:+-tags=${lib.concatStringsSep "," tags}} ''${ldflags:+-ldflags="$ldflags"} -v -p $NIX_BUILD_CORES $d 2>&1)"; then
+        if ! OUT="$(go $cmd "''${flags[@]}" $dir 2>&1)"; then
           if ! echo "$OUT" | grep -qE '(no( buildable| non-test)?|build constraints exclude all) Go (source )?files'; then
             echo "$OUT" >&2
             return 1
@@ -225,7 +235,7 @@ let
       runHook preCheck
 
       for pkg in $(getGoDirs test); do
-        buildGoDir test $checkFlags "$pkg"
+        buildGoDir test "$pkg"
       done
 
       runHook postCheck