glib: Fix compilation on Darwin and use default gcc

http://hydra.nixos.org/build/12458779

pkgs/development/libraries/glib/default.nix

@@ -49,6 +49,8 @@ stdenv.mkDerivation rec {
     sha256 = "1d98mbqjmc34s8095lkw1j1bwvnnkw9581yfvjaikjvfjsaz29qd";
   };
 
+  patches = optional stdenv.isDarwin ./darwin-compilation.patch;
+
   setupHook = ./setup-hook.sh;
 
   buildInputs = [ libelf ]
@@ -67,6 +69,11 @@ stdenv.mkDerivation rec {
   NIX_CFLAGS_COMPILE = optionalString stdenv.isDarwin " -lintl"
     + optionalString stdenv.isSunOS " -DBSD_COMP";
 
+  preBuild = optionalString stdenv.isDarwin
+    ''
+      export MACOSX_DEPLOYMENT_TARGET=
+    '';
+
   enableParallelBuilding = true;
 
   inherit doCheck;