This is a feature that was added in rpm-ostree 2023.10 and is needed
for the new transient /etc feature to work. What it does is change the
labeling of /usr/etc to match those of /etc, so that /usr/etc can be used
directly as a bind-mount or an overlay mount when mounted on /etc.
See https://github.com/coreos/rpm-ostree/pull/4640 for details.