We forgot to set two version related ldflags in our packaging and this
should prevent this from going unnoticed again.
Further details are in dab7aa20ed.
This should allow us to catch issues regarding that in the future.
nixos/gitea had an issue with the dump service recently, which didn't
affect us, fortunately.
But to be fair, it only affected non-default-y setups.
Not something we are able to catch in the current, rather simple, config
of our test.
Still, I see a lot of value adding this new subtest to our test suite.
Anyhow, this patch also exposes the resulting tarball as test (build)
output, which is a nice addition IMHO, as it allows some sort of
external sanity-check, if needed, without running the test interactive.
