Merge staging into closure-size

The most complex problems were from dealing with switches reverted in
the meantime (gcc5, gmp6, ncurses6).
It's likely that darwin is (still) broken nontrivially.

pkgs/development/compilers/mkcl/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchgit, gmp }:
+{ stdenv, fetchgit, makeWrapper, gmp, gcc }:
 
 stdenv.mkDerivation rec {
   v = "1.1.9";
@@ -10,6 +10,7 @@ stdenv.mkDerivation rec {
     sha256 = "0ja7vyp5rjidb2a1gah35jqzqn6zjkikz5sd966p0f0wh26l6n03";
   };
 
+  buildInputs = [ makeWrapper ];
   propagatedBuildInputs = [ gmp ];
 
   configureFlags = [
@@ -17,6 +18,10 @@ stdenv.mkDerivation rec {
     "GMP_LDFLAGS=-L${gmp.out}/lib"
   ];
 
+  postInstall = ''
+    wrapProgram $out/bin/mkcl --prefix PATH : "${gcc}/bin"
+  '';
+
   meta = {
     description = "ANSI Common Lisp Implementation";
     homepage = https://common-lisp.net/project/mkcl/;