Due to a previous bug in the makefiles, debhelper didn't actually
install anything relevant (as the install target bailed even during a
dry-run). Prevent this from happening again by being very specific about
what gets installed and fail the package build process in case of
unexpected files.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Guillaume Desmottes <guillaume.desmottes@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D5250