RISC-V support

[RaitoBezarius]

I want SecureBoot on RISC-V, that's all.

[RaitoBezarius]

• OVMF support in nixpkgs
• QEMU test support
• Lanzatool/Lanzaboote support

[RaitoBezarius]

I will receive my VF2 on 5 Jan. apparently, will see how hard is it to setup at least a remote builder for software and even a testbed (???).

[sreehax]

Part of the trouble will be in compiling rust onto riscv uefi. I have tried this in the past, and the issue I ran into was that LLVM did not seem to want to build a RISC-V PE/COFF object file at all. The only workarounds for this are either 1. fix LLVM or 2. actually create a riscv ELF binary, but create a faux COFF header with assembly that jumps to the ELF code. This is what the linux kernel uses to boot as EFISTUB on arm64. All of this work will probably fall onto uefi-rs (rust-osdev/uefi-rs#241).
References:
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kernel/head.S
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arch/arm64/booting.rst