To make it clearer to users when synchronization behaviour is not supported, return ENOTSUP when O_RSYNC, O_DSYNC or O_SYNC are respectively not defined. Linux also doesn't support O_RSYNC despite the O_RSYNC flag being defined.
To make it clearer to users when synchronization behaviour is not supported, return ENOTSUP when O_RSYNC, O_DSYNC or O_SYNC are respectively not defined. Linux also doesn't support O_RSYNC despite the O_RSYNC flag being defined.