[bug#27705] [PATCH v4 4/4] vm: Use grub-hybrid's grub-mkrescue.

[Danny Milosavljevic]

Pushed this patch to master as ba4de3b3ef07a95f8a610cdc5354de554b7a4a6b.

This means that these work now:

$ cp `guix system disk-image -t iso9660 gnu/system/install.scm` Z
$ qemu-system-x86_64 -bios $(guix build ovmf)/share/firmware/ovmf_x64.bin -m 1G 
-enable-kvm -cdrom Z -serial stdio
$ qemu-system-x86_64 -m 1G -enable-kvm -cdrom Z -serial stdio

And these don't work (as in: guest kernel crashes because it can't find the 
root):

$ cp `guix system disk-image -t iso9660 gnu/system/install.scm` Z
$ chmod +w Z
$ qemu-system-x86_64 -bios $(guix build ovmf)/share/firmware/ovmf_x64.bin -m 1G 
-enable-kvm -hda Z -serial stdio
$ qemu-system-x86_64 -m 1G -enable-kvm -hda Z -serial stdio

That's because "[PATCH v4 2/4] build: Allow mounting of entire disks" is not 
applied.  What do we do about it?  Should we apply it, too?