beret: Fix build on darwin (close #923)

pkgs/games/beret/default.nix

@@ -6,8 +6,9 @@ stdenv.mkDerivation {
   buildInputs = [ SDL SDL_image SDL_ttf SDL_mixer ];
 
   NIX_CFLAGS_COMPILE = "-I${SDL}/include/SDL";
-
-  NIX_CFLAGS_LINK = "-lgcc_s";
+  NIX_CFLAGS_LINK = stdenv.lib.optionalString (!stdenv.isDarwin) "-lgcc_s";
+  NIX_LDFLAGS = stdenv.lib.optionalString stdenv.isDarwin
+    "-framework CoreFoundation -framework OpenGL -framework Cocoa";
 
   patches = [ ./use-home-dir.patch ];
 
@@ -28,11 +29,12 @@ stdenv.mkDerivation {
     cp -av tahoma.ttf images music rooms sfx $out/share
   '';
 
-  meta = {
+  meta = with stdenv.lib; {
     description = "A 2D puzzle-platformer game about a scientist with telekinetic abilities";
-    homepage = http://kiwisauce.com/beret/;
-    platforms = stdenv.lib.platforms.all;
-    license = stdenv.lib.licenses.lgpl2;
+    homepage    = http://kiwisauce.com/beret/;
+    license     = licenses.lgpl2;
+    maintainers = with maintainers; [ lovek323 ];
+    platforms   = platforms.all;
   };
 }