PR pipeline: install the package to mock

[Miro Hrončok]

Hey CIers!

I need to do the following on the PR pipeline:

1. dnf install mock (I know how)
  2. mock -r fedora-rawhide-x86_64 init (should work)
  3. mock -r fedora-rawhide-x86_64 <package_form_ci_koji_scratchbuild> (no idea)
  4. various package builds in that mock (no problem)

Could you please help me with 3?

The package should be installed on the system so I might be able to salvage it 
from the dnf cache, but I'm not sure if that it reliable.

Thanks,