bluez/ubt: Add execution permission

ubt from git is not executable. It must be chmoded frequently.
Let's change that!

Reviewed-by: Philip Withnall <philip.withnall@collabora.co.uk>
Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.com>
Differential Revision: https://phabricator.apertis.org/D5052