Packit: fix build issue on Fedora Rawhide
Packit: fix build issue on Fedora Rawhide

If the `source_date_epoch_from_changelog` is set to true,
the `SOURCE_DATE_EPOCH` environment variable is set to the timestamp
of the topmost changelog entry. As we do not have a changelog
in the upstream spec file we auto generate it.

OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap