🐞 Workaround Fedora problems created by rpm commit 93604e2 take 2
    (backwards-incompatible)
    
    This “minimal” workaround forces the computation and setting of all the
    preamble variables that MAY be used in Source/Patch declarations before the
    Source and Patch lines are processed by the rpm parser, as imposed by the rpm
    change.
    
    Like the rpm change, it is not backwards-compatible. It REQUIRES modification
    of all existing font spec files.
    
    See also:
    https://github.com/rpm-software-management/rpm/issues/1161
    https://pagure.io/packaging-committee/issue/968
    https://bugzilla.redhat.com/show_bug.cgi?id=1820349
    https://bugzilla.redhat.com/show_bug.cgi?id=564613