bug#47889: [installer image] grub-install efi fails getting canonical path to /boot/efi on dos-formatted disk

[Mathieu Othacehe]

Hello,

> Regarding the MSDOS/UEFI patch, it is almost identical to what Florian
> tested. I chose not to force GPT on UEFI if the user disk is already
> MBR formatted, mostly to keep the code readable.

Pushed on master and cherry-picked on version-1.3.0 branch.

Thanks,

Mathieu