Add multimedia pack to Jenkins builds

Enable download of multimedia pack from:
https://images.apertis.org/media/multimedia-demo.tar.gz



Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D7418