Modification would be: guix/scripts/system.scm install-bootloader should resolve target, like
if target doesn't startwith "/dev/"
compare target with ID_SERIAL using udevinfo, return device name
else
as before
gnu/system/vm.scm qemu-image should resolve target likewise before calling
initialize-hard-disk.
I wonder how qemu drive serial numbers work.
https://serverfault.com/questions/318755/qemu-can-i-set-the-serial-number-on-a-virtual-scsi-device
