testsuite: compress modules if feature is enabled

testsuite: compress modules if feature is enabled

Since the output needs to be the same, regardless if the module is
compressed, change populate-modules.sh to conditionally compress the
module if that feature is enabled.

This way we can execute the tests with any build-time configuration and
it should still pass.

Suggested-by: Michal Suchánek <msuchanek@suse.de>
Reviewed-by: Michal Suchánek <msuchanek@suse.de>
Tested-by: Michal Suchánek <msuchanek@suse.de>
Reviewed-by: Petr Vorel <pvorel@suse.cz>