buildroot

rootfs-overlay: also exclude .empty files

This makes it possible to put empty directories in the overlay.
Thanks to Aras Vaichas for pointing that out.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>