[`pacman-init.service`](configs/releng/airootfs/etc/systemd/system/pacman-init.service) hardcodes the `archlinux` keyring. There should be no need to do that. If it's omitted and run as `pacman-key --populate`, it will use all of the keyrings from `/usr/share/pacman/keyrings/`. This would simplify adapting `releng` for ISOs that ship with custom pacman keyrings.