We'll think it over for how we want to handle custom reboot commands,
but some platforms (e.g. u-boot, depthcharge, qemu) don't and can't use
them.
A goal is to keep stage-2 as generic as possible, so building into it
some knowledge of this is harder.
At any rate, the user can still reboot, and hold the key combo as
needed!
The examples/hello system can be used by users that want to boot a
minimal, and cross-compilable system.
This is better than a "raw" build of the root of the Mobile NixOS repo
since it provides a stage-2 application stating the system booted
successfully.
