buildFHSEnv: add standard paths for compilers

pkgs/build-support/build-fhs-chrootenv/env.nix

@@ -57,6 +57,11 @@ let
     export LOCALE_ARCHIVE='/usr/lib/locale/locale-archive'
     export LD_LIBRARY_PATH='/run/opengl-driver/lib:/run/opengl-driver-32/lib:/usr/lib:/usr/lib32'
     export PATH='/var/setuid-wrappers:/usr/bin:/usr/sbin'
+
+    # Force compilers to look in default search paths
+    export NIX_CFLAGS_COMPILE='-idirafter /usr/include'
+    export NIX_LDFLAGS_BEFORE='-L/usr/lib -L/usr/lib32'
+
     ${profile}
   '';