fanotify.7: Allow relative paths in example

The current example code requires passing an absolute
path to the mount to be watched.

By passing AT_FDCWD to fanotify_mark it can use both
absolute and relative paths.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/fanotify.7

@@ -691,7 +691,7 @@ main(int argc, char *argv[])
          file descriptor */
 
     if (fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_MOUNT,
-                      FAN_OPEN_PERM | FAN_CLOSE_WRITE, \-1,
+                      FAN_OPEN_PERM | FAN_CLOSE_WRITE, AT_FDCWD,
                       argv[1]) == \-1) {
         perror("fanotify_mark");
         exit(EXIT_FAILURE);