treewide: disable sdl-config darwin time outs

sdl-config has an issue on hydra where it will hang when run on
Darwin. This is probably related to the headless mode that is set up &
the sdl-config program waiting for a graphical to finish.

pkgs/games/freedink/default.nix

@@ -54,5 +54,6 @@ in stdenv.mkDerivation rec {
 
     maintainers = [ stdenv.lib.maintainers.bjg ];
     platforms = stdenv.lib.platforms.all;
+    hydraPlatforms = stdenv.lib.platforms.linux; # sdl-config times out on darwin
   };
 }