mosml: pass -fpermissive to C compiler

The MosML build system relies on some terrible C that GCC 14 now
refuses to compile. This has supposedly been fixed in MosML upstream,
but the fix is not yet in any released version. It is not so easy to
simply cherry-pick the changes necessary to make GCC 14 work, since
they seem spread over various different commits. This change serves to
make this rather obscure derivation work for a little while longer.

pkgs/by-name/mo/mosml/package.nix

@@ -20,6 +20,8 @@ stdenv.mkDerivation rec {
     "CC=${stdenv.cc.targetPrefix}cc"
   ];
 
+  env.NIX_CFLAGS_COMPILE = "-fpermissive";
+
   src = fetchFromGitHub {
     owner = "kfl";
     repo = "mosml";