apps: Add strip_source_version_suffix support
This is necessary for packages that were built in OBS which adds a suffix,
but the source isn't kept, and is identical to the base version except
for debian/changelog.
This is already done for runtimes.
Add Python dependency to SDK to be able to use the same variable for both
runtimes and apps.
Signed-off-by: Frédéric Danis frederic.danis@collabora.com