If permission is the problem, and you can't figure out any other way, you can add the below lines into your build file, that'll change the permission of the new file to 777 everytime whe you run build!! Don't use this unless ur desperate, since it's very cheap way and forcing the permissions:)
#chmod
chmod (0777, "$build_root_url/New/new.html");
#chmod
chmod (0777, "$build_root_url/New/new.html");