gitlab CI: build an rpm package to verify the installed file list
This is not a package intended for, it's a job to fail when we accidentally change the file list. An rpmbuild job like this was what detected f15da0f1.
The spec file resembles the Fedora one but has BuildRequires removed (we rely on the container for that).
The same task could be achieved by keeping a file list and comparing the installed tree but since I had the rpm spec file already, let's use that for now.
Marking as WIP - merge once meson 0.55 is in Fedora 32, then rebuild the images so we don't need to pip install it. meson 0.55 is required for the --no-test
option