require systemd-rpm-macros rather than systemd
    
    The `BuildRequires: systemd` was added in d7389e7 (use systemd instead
    of xinetd (bz 737183), 2013-04-30).  Since then, the systemd macros have
    been split into a subpackage¹.  Adjust our BuildRequires (with an
    exception for EL-7).
    
    Replace `Requires*: systemd` in git-daemon with %{?systemd_requires}.
    
    ¹ https://src.fedoraproject.org/rpms/systemd/c/c9030f0 (Split out the
      rpm macros into systemd-rpm-macros subpackage, 2018-11-02),