After commit a0933cd17d19, access(_, X_OK) returns 0 if the user
holds SE_BACKUP_PRIVILEGE, even if the file's ACL denies execution
to the user. This is triggered by trying to open the file with
FILE_OPEN_FOR_BACKUP_INTENT.
Fix check_file_access() so it checks for X_OK without specifying
the FILE_OPEN_FOR_BACKUP_INTENT flag if the file is not a directory.
Rearrange function slightly and add comments for easier comprehension.
Fixes: a0933cd17d19 ("Cygwin: access: Correction for samba/SMB share")
Reported-by: Bruno Haible <bruno@clisp.org>
Co-authored-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
2e4db338ac