Make systemd-devel conditionally pull in systemd-rpm-macros
    
    If people BR:systemd-devel, they should get the macros too. It's a
    tiny package, and we shouldn't require people to BR two things.
    
    https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/A5BGKRZVFDOBNMCBUPUCKLKHWEW5V2JE/