gcc: minimal hacky fixup for our pkgsi686Linux.nix

This has been blocking nixos-unstable channel through i686 ISO:
Fixes #82435, closes #82436.
https://hydra.nixos.org/build/114512204

pkgs/development/compilers/gcc/9/default.nix

@@ -245,6 +245,12 @@ stdenv.mkDerivation ({
 
   inherit (stdenv) is64bit;
 
+  # In this particular combination it stopped creating lib output at all.
+  # TODO: perhaps find a better fix?  (ideally understand what's going on)
+  postFixup = if crossStageStatic && targetPlatform.isMusl && targetPlatform.isi686
+    then ''mkdir "$lib"''
+    else null;
+
   meta = {
     homepage = https://gcc.gnu.org/;
     license = stdenv.lib.licenses.gpl3Plus;  # runtime support libraries are typically LGPLv3+