Avoid spending ~100ms of userspace boot time on unnecessary regeneration
of entirely static /etc/{passwd,group,shadow}. This will be proposed to nixpkgs.
Relying on udev to assign permissions to the virtgpu was very "proper"
but really excessive. We have a simple static configuration, built into
the kernel, so there are no dynamic shenanigans, we can always reliably
just chmod/chown the permissions. Let's go back to faster booting.
