The `set -euo pipefail` shouldn't be controversial.
The `set -x` bit is more debatable because it makes
the output more verbose but I find it helpful right
now as I comb through all sorts of details as part of
https://github.com/coreos/fedora-coreos-tracker/issues/1861.
If we care about less verbose output, I'd prefer we keep `-x` but
switched to having rpm-ostree buffer postprocess output and only dump it
if it fails.
