Generate RPM package version from git tags

Summary

As briefly discussed in https://gitlab.cern.ch/cmsgemonline/cmsgemos/-/merge_requests/43#note_3739268, there is no straightforward way to use the git tags to include the version inside the SRPM with git-archive. An external tool such as tito is likely the way to go to easily implement such a feature in a robust way.

What is the expected correct behavior?

The RPM version number is based on the git tag.