About add installer EFI partition support

[sxueck]

https://github.com/nerun/remastersys/blob/458fcbb41c4cd4f405385f435332207725c6c8a4/remastersys/usr/bin/remastersys-installer#L110

When doing an iso restore, I noticed that it was not booting correctly through UEFI (including when I actually tested it), but I solved the problem manually, which may help you a bit

1. Create UFI partition : fdisk /dev/sdb (n 1 enter +512M t [EFI System] w)
2. sudo apt-get install dosfstools
3. format it: sudo mkfs.fat -F32 /dev/sdb1
4. mount: sudo mount /dev/sdb1 /boot/efi
5. sudo grub-install /dev/sdb --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB
6. echo "/dev/sdb1 /boot/efi vfat defaults 0 1" | sudo tee -a /etc/fstab

PS: /dev/sdb is boot system disk

There may be times when this boot is not shown in the bios, you can try add the boot option

DELL BIOS Examples