0verkill: fix darwin build

pkgs/games/0verkill/default.nix

···
 { lib
-, stdenv
+, gccStdenv
 , fetchFromGitHub
 , autoreconfHook
 , xorgproto
···
 , libXpm
 }:
 
-stdenv.mkDerivation rec {
+gccStdenv.mkDerivation rec {
   pname = "0verkill";
   version = "unstable-2011-01-13";