Build: Fix out of tree build issues for some repo

Current configuration only allows libmetal, open-amp and psa-adac
repositories to be build in source tree.
Update the configuration so that can be built out of source tree
and don't have to be cloned/downloaded if explicit path is provided.

Signed-off-by: Maulik Patel <maulik.patel@arm.com>
Change-Id: Iac306de683688a9e0d2ee5c3328ca71b019b5b9e
3 files changed