etc: remove unneeded temporary directions after putting in place the new etc

        # Unmount the top /etc mount to atomically reveal the new mount.

        umount --lazy --recursive /etc

        # Unmount the temporary mount

        umount --lazy "$tmpEtcMount"

        rmdir "$tmpEtcMount"

        # Unmount old metadata mounts

        # For some reason, `findmnt /tmp --submounts` does not show the nested

        # mounts. So we'll just find all mounts of type erofs and filter on the

        # name of the mountpoint.

        findmnt --type erofs --list --kernel --output TARGET | while read -r mountPoint; do

          if [[ "$mountPoint" =~ ^/tmp/nixos-etc-metadata\..{10}$ &&

                "$mountPoint" != "$tmpMetadataMount" ]]; then

            umount --lazy $mountPoint

            rmdir "$mountPoint"

          fi

        done

      fi

    '' else ''

      # Set up the statically computed bits of /etc.