Add empty directory 'overlays/armhf-target'

Add empty directory to allow to work 'overlay' action for armhf.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D7254