Changed ruby version to 2.7.x to match upstream.
Added a gem config for gitlab-pg_query as it tries to download a source
tarball during the build process.
Also removed a patch for gitaly that has become obsolete by upstream fix
[here](de04077c25).
- gitlab-shell no longer requires ruby for anything else than the
install script, so the bundlerEnv stuff could be dropped
- gitlab-shell and gitlab-workhorse now report their versions
correctly
Instead of extracting prebuilt assets from the debian build, build
them from the source. This should give faster package updates and
reduces the amount of data needed to be downloaded by more than 500MB.