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/freeciv/default.nix

@@ -51,5 +51,6 @@ stdenv.mkDerivation {
 
     maintainers = with maintainers; [ pierron ];
     platforms = platforms.unix;
+    hydraPlatforms = stdenv.lib.platforms.linux; # sdl-config times out on darwin
   };
 }