Interest check: U-Boot bootloader support

[Jookia]

Hey there,

I brought up this topic a long time ago and as since have been thinking about
this, reading the code base and getting accustomed to it. I've had the intention
of porting GuixSD to use the U-Boot bootloader, which I think can be done
without much if any changes to the user-facing configuration.

I'm willing to do the refactor and programming required, but I'm sensing it's
not wanted given the investment in keeping GuixSD using GNU tools for the base
system and the fact GRUB is being ported to ARM (though this is buggy at best.)
The only thing U-Boot support brings to the table is that it works and can be
used to boot Linux on an ARM system. The only hindrance compared to GRUB is that
it doesn't support encrypted partitions, so unencrypted /boot support will need
to be added.

If there's no interest in having U-Boot support in Guix and upstreamed, I'd
rather not waste effort on writing these patches. No hard feelings!

Cheers,
Jookia.