Verify mandatory Ruby patches exist
What does this MR do and why?
This change ensures that all Ruby patches necessary to correctly run GitLab exist and are applied when building the image.
This should prevent incidents like gitlab#384081 (closed) from happening because we catch missing patches in CI.
The list of mandatory patches is a flat file, with each patch name on a separate line. I am not sure how or where to best document this since there is only one entry in the file currently.
Here is an example of how this would now fail:
Edited by Matthias Käppler