I am unsure exactly what situation is causing the loopback partition
device node to not exist when it is being mounted but this should help
work around the situation and log loudly about it so we can hopefully
figure out where to dig further.
This script replaces the standard grub-install tool to give us some more
control over what is going and ensure grub-install's auto-detection
magic doesn't make any incorrect choices. Also this script sets up a
loopback device and mounts the EFI partition in just the right way for
grub-bios-setup's auto-detection magic to work correctly.
I've chosen not to adapt disk_util to use partitioned loop devices to
make grub happy because ensuring loop devices get cleaned up properly
for the general case gets tricky and less robust.
