// the file descriptor dirfd. If name is anything but a directory (this
// includes a symlink to one), it should return an error. Other than that this
// should act like openFileNolog.
//
// This acts like openFileNolog rather than OpenFile because
// we are going to (try to) remove the file.
// The contents of this file are not relevant for test caching.
func openDirAt(dirfd int, name string) (*File, error) {