The big rewrite of rhel9 distro omitted installing s390utils-base into the
buildroot. This caused the org.osbuild.zipl.inst stage because of missing
/usr/sbin/zipl.
This commit introduces s390utils-base back into the buildroot which fixes
building of the s390x images.
I verified it by building the RHEL 9.1 qcow2 image and booting it using
libvirt.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>