Due to missing `/etc/machine-id` in the new root, systemd-tmpfiles
outputs a bunch of scary warnings like "Failed to replace specifiers in
'/run/log/journal/%m'". We only care about /tmp, so hide them.
`-E` is an alias for `--exclude-prefix=/dev --exclude-prefix=/proc
--exclude-prefix=/run --exclude-prefix=/sys`.
a5b7b6e47a