Switch to xorriso (instead of genisoimage)
Upstream prefers it since:
commit 174a0caf7eaf1943360f9d8f714f466ea7449d90
Author: Richard W.M. Jones <rjones@redhat.com>
Date: Sat Apr 3 17:15:34 2021 +0100
iso: Pick xorriso in preference to genisoimage or mkisofs.
See this Debian page explaining the situation with genisoimage:
https://wiki.debian.org/genisoimage