Reuse gitlab cache when building

To test this MR we would need to merge it into main.
I will be off now, so we can do it either tomorrow, or you can revert if this merge behaves wrong.

Changes: all builds are now done in one job to make it easier to add new flavors.

Anyhow we should wait until https://gitlab.com/recoverycat/rcc-client/-/pipelines/993344895 has succeeded to check the other change was successful. which will be obsolete after this merge though. The pipeline failed but the next one was ok 🤷