Adding alma9 runners to CI

I have tried to add one new CI runner to our CI, but it fails immediately: https://gitlab.cern.ch/cta/CTA/-/jobs/29570000

The problem is that some part of gitlab-ci are assuming that CI is running as root and alters the runner in ways that are forbidden:

Our CI scripts are working fine, but we need fixes for the common gitlab environment setup. I guess these changes were made for containers and with the refactor they propagated to the kubernetes runners.

We should make sure that these changes are only applied where they should.

This was already bad with a CC7 runner that overwrote its repositories with the one of the CC7 CI container, but now that the CI runner is running Alma9: copying/configuring some CC7 repositories on a Alma9 is even more deadly...