haskellPackages.c2hs: Disable tests on Darwin

The tests require gcc, but gcc is no longer available on Darwin systems.

pkgs/development/haskell-modules/configuration-common.nix

@@ -48,6 +48,7 @@ self: super: {
   text_1_2_0_4 = dontCheck super.text_1_2_0_4;
   text_1_2_0_6 = dontCheck super.text_1_2_0_6;
   text = dontCheck super.text;
+  c2hs = if pkgs.stdenv.isDarwin then dontCheck super.c2hs else super.c2hs;
 
   # The package doesn't compile with ruby 1.9, which is our default at the moment.
   hruby = super.hruby.override { ruby = pkgs.ruby_2_1; };