corosync.spec: Add system-devel build requirement

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Ferenc Wágner <wferi@debian.org>

corosync.spec.in

@@ -63,6 +63,7 @@ BuildRequires: dbus-devel
 %endif
 %if %{with systemd}
 BuildRequires: systemd-units
+BuildRequires: systemd-devel
 Requires(post): systemd
 Requires(preun): systemd
 Requires(postun): systemd