mtools: fix build on darwin

pkgs/tools/filesystems/mtools/default.nix

@@ -8,12 +8,19 @@ stdenv.mkDerivation rec {
     sha256 = "119gdfnsxc6hzicnsf718k0fxgy2q14pxn7557rc96aki20czsar";
   };
 
+  # Prevents errors such as "mainloop.c:89:15: error: expected ')'"
+  # Upstream issue https://lists.gnu.org/archive/html/info-mtools/2014-02/msg00000.html
+  patches = stdenv.lib.optional stdenv.isDarwin ./UNUSED-darwin.patch;
+
+  # fails to find X on darwin
+  configureFlags = stdenv.lib.optional stdenv.isDarwin "--without-x";
+
   doCheck = true;
 
   meta = {
     homepage = http://www.gnu.org/software/mtools/;
     description = "Utilities to access MS-DOS disks";
-    platforms = stdenv.lib.platforms.gnu;  # arbitrary choice
+    platforms = stdenv.lib.platforms.gnu ++ stdenv.lib.platforms.darwin;
     maintainers = [ ];
   };
 }