Hello Guix,

I'm using a Guix system with the efi-bootloader-chain [1]. The chain
loads m1n1 (the Asahi Linux boot loader), u-boot and then grub.

A system roll-back used to work fine, but it stopped to work a while
ago. I'm not sure when that happened, because I rarley needed to
roll-back. But now that I don't have it anymore, I'm a bit nervous.

When I do a roll-back, this is what happens:

```
$ sudo guix system roll-back
Password:
guix system: error: efi-bootloader-chain: no such bootloader
```

It looks like the efi-bootloader-chain can't be found in the
%bootloaders variable of the (gnu bootloader) module. But that seems
strange, since it is defined in the same file (just a bit later).

Any ideas?

Thanks, Roman.

[1] https://github.com/asahi-guix/channel/blob/main/modules/asahi/guix/bootloader/m1n1.scm