Add "arrch64-darwin" to badPlatforms

Aarch64-darwin is not supported for chez.

pkgs/development/compilers/chez/default.nix

···
     license      = lib.licenses.asl20;
     maintainers  = with lib.maintainers; [ thoughtpolice ];
     platforms    = lib.platforms.unix;
-    badPlatforms = [ "aarch64-linux" ];
+    badPlatforms = [ "aarch64-linux" "aarch64-darwin" ];
   };
 }