package-source-builder: ci-buildpackage: Never create orig tarballs

If for any reason git-buildpackage fails to detect the orig tarball extracted from the pristine-lfs branch it tries to generate it using pristine-tar or git archive.

This is not desirable, we definitely prefer erroring out in case something goes wrong as we always want to rely on pristine-lfs to ensure that the orig tarballs are bit-identical to the upstream ones.