choose and setup infrastructure to build RPMs (e.g. for branding packages)

At least for branding tracked in #28, EU OS needs a place to build RPMs.

I don't know if one could build them directly in Gitlab and then use them in the blue-build pipeline on Gitlab. This would be best as it reduces the number of services EU OS relies on.

If Gitlab cannot be used, alternatives could be:

• fedora infrastructure (branching from https://src.fedoraproject.org/rpms/generic-logos / project namespace in https://copr.fedorainfracloud.org/coprs )
• opensuse build service with fedora support

If/when EU OS approaches production, one could of course do self-hosting, but at this stage it seems to be to complex.