leanify: mark darwin as broken

See https://github.com/NixOS/nixpkgs/pull/223300#discussion_r1148651152

Co-authored-by: Weijia Wang <9713184+wegank@users.noreply.github.com>

pkgs/tools/misc/leanify/default.nix

@@ -35,5 +35,6 @@ stdenv.mkDerivation rec {
     license = licenses.mit;
     maintainers = [ maintainers.mynacol ];
     platforms = platforms.all;
+    broken = stdenv.isDarwin;
   };
 }