Detect Grub target in use.

[vbence]

By default Grub will install the bootloader (UEFI, or MBR) which was used to boot the current environment.

This information have to be made available to the restore script, which can then use the --target parameter to force the right installation method.

[vbence]

Method will be:
http://unix.stackexchange.com/a/178027/23586

Not the sweetest solution though - involves some guesswork.

[vbence]

The following line should guess the right value pretty accurately:

comm -12 <(find /boot/grub -name moddep.lst | sed -r "s/^.*\/([^\/]+)\/.+$/\1/g") <(find /usr/lib/grub -name moddep.lst | sed -r "s/^.*\/([^\/]+)\/.+$/\1/g")