stdenv: Fix gcc -idirafter shell glob in cc-wrapper

If an empty string is passed to `-idirafter`, it breaks gcc. This commit makes
the stdenv less fragile by expanding out the shell glob and ensuring no empty
arguments get passed.

pkgs/build-support/cc-wrapper/default.nix

@@ -235,7 +235,7 @@ stdenv.mkDerivation {
       fi
     ''
 
-    + optionalString (libc != null) ''
+    + optionalString (libc != null) (''
       ##
       ## General libc support
       ##
@@ -251,11 +251,17 @@ stdenv.mkDerivation {
       # compile, because it uses "#include_next <limits.h>" to find the
       # limits.h file in ../includes-fixed. To remedy the problem,
       # another -idirafter is necessary to add that directory again.
-      echo "-B${libc_lib}${libc.libdir or "/lib/"} -idirafter ${libc_dev}${libc.incdir or "/include"} ${optionalString isGNU "-idirafter ${cc}/lib/gcc/*/*/include-fixed"}" > $out/nix-support/libc-cflags
+      echo "-B${libc_lib}${libc.libdir or "/lib/"}" >> $out/nix-support/libc-cflags
+      echo "-idirafter ${libc_dev}${libc.incdir or "/include"}" >> $out/nix-support/libc-cflags
+    '' + optionalString isGNU ''
+      for dir in "${cc}"/lib/gcc/*/*/include-fixed; do
+        echo '-idirafter' ''${dir} >> $out/nix-support/libc-cflags
+      done
+    '' + ''
 
       echo "${libc_lib}" > $out/nix-support/orig-libc
       echo "${libc_dev}" > $out/nix-support/orig-libc-dev
-    ''
+    '')
 
     + optionalString (!nativeTools) ''
       ##