Create a 300 MiB EFI system partition.
Install GRUB to the default/fallback boot path on the ESP. This way it will boot everywhere and NVRAM will not be touched.
- dosfstools is needed for fsck.vfat,
- efibootmgr is for manipulating UEFI boot entries. This is not done by any of scripts since we don't want to touch NVRAM.
Implements #141 (closed)
Depends on !179 (merged).