Changes

release-tarball-build-dist: order install pkgs

Change-Id: I059f400db20e858b379704363e32d39a7897984a

release-tarball-build-dist: move rsync into docker

Prepare to use ssh inside the docker container to check if tarballs
already exist, see the next patch.

Remove the '' around UserKnownHostsFile as using SSH_COMMAND in the next
patch without rsync fails otherwise with:
  command-line: line 0: Bad configuration option: 'userknownhostsfile

Change-Id: I6dfe5d587d05063c6cf2c9ec683e7b7e499b79c1

release-tarball-build-dist: check exists on server

Previously this job relied on always running on the same jenkins node,
and having the previously built release tarballs in a workspace
directory that does not get removed. It would only skip building a
release tarball if the file already exists locally.

As part of OS#5793 this job needs to be moved away from that jenkins
node. When trying to run the job on a different node, it will build all
release tarballs again which takes unnecessarsily long and actually
fails on libosmocore-0.9.4 due to a missing python2.

This probably happens because the job was refactored at some point and I
didn't realize that the python2 dep is now missing as the previous
tarballs existed.

In general it doesn't make much sense to build previous release tarballs
again and to always keep the legacy environments around for that. Change
the code to check if a tarball exists on the server, and skip building
the tarball in that case.

Related: OS#5793
Related: https://jenkins.osmocom.org/jenkins/view/All%20no%20Gerrit/job/Osmocom-release-tarballs/1281/console
Change-Id: I4b8c149c9cdbe7c613eea5d9be15794de5e5ddce

release-tarball-build-dist: fix missing dir crash

Don't fail if no tarball was generated and therefore the
_release_tarballs directory does not exist.

Related: OS#5793
Change-Id: Ib7c551e5376776eb267140bc4b897d5bb1634cbc

release-tarball-build-dist: fix permission errors

Run all commands inside the docker containers as a user with the same
UID as on the host system, not as root. This is a good idea in general
and also fixes permission problems when jenkins tries to wipe the
workspace.

Related: OS#5793
Change-Id: I0d949e5ab4b1a709d18a316def0a98c3b244457e