We accidentally checked if the DIRECTORY is of type OS_FILE_TYPE_UNKNOWN; our intention was to check if the FILE is that; best to remove the check altogether, as in crash recovery it is safest to try to open also files whose type is unknown
os0file.c:
  Fix a bug: in Windows, os_file_readdir_next_file() returned OS_FILE_TYPE_UNKNOWN as the type of a regular file; this did not break mysqld, but did break ibbackup on Windows