uefi_multiboot: create UEFI-compatible images

uefi_multiboot:  Create UEFI-compatible boot drive supporting multiple ISO images.

It requires UEFI-based target systems, and Ubuntu-system to build, and a disposable USB drive (everything on drive will be deleted).

https://github.com/sundarnagarajan/uefi_multiboot

(Someone looking to create a script that generates a UEFI boot drive could also benefit from using parts of this script.)