Build as a UEFI binary

[obbardc]

This would allow us to reflash images without having to boot into a Linux system.
Using https://github.com/rust-osdev/uefi-rs we could build for all architectures, i686, x86_64, or aarch64

In the first case, just launching the bmap binary from a UEFI shell in qemu would be great progress.
We could add a follow-up task to show how to build a "custom" UEFI program that does something specific e.g. downloads an image from HTTP in UEFI.

[obbardc]

This will need some careful thinking about, since the EFI environment is entirely different from running under Linux. The API functions for writing to files and block devices may be completely different. Networking may also need to be investigated.

[sjoerdsimons]

fwiw the first step to do for that is to make/keep the library crate build in a no_std environment; Which opens up the possibility to write a uefi app using it as there is no std lib support for uefi (yet); I have not validate if all current crates allow a no_std build fwiw

[obbardc]

relevant example: https://gitlab.com/aruiz/rust-uefi-example