Use newest arm64 UEFI and amd64 OVMF CODE/VARS firmware

[damdo]

This PR updates the arm64 UEFI firmware to a version newer than 2023.11, as running on qemu >= 9.0 can trigger a bug in the older versions of the EDK2 guest firmware, causing Synchronous Exception and potential bootloops.
See: #80

While doing so it updates the amd64 OVMF firmware, which now has removed support for the 2M firmware and only supports the 4M one. The 4M OVMF firmware comes with split CODE and VARS images, which need to be loaded as pflash drives in the qemu vm, rather than via the -bios flag.

For more details on the migration see: https://salsa.debian.org/qemu-team/edk2/-/blob/debian/latest/debian/howto-2M-to-4M-migration.md

Fixes #80

[stapelberg]

Thank you! I verified that this works in QEMU 9 on my machine (which is what I typically use).

I don’t have an older QEMU handy, but using nix-shell and an older version of nixpkgs allowed me to test with QEMU 7 and indeed it works (with --arch=arm64 and without):

% nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-22.05.tar.gz -p qemu
[nix-shell:~/gokrazy/virtual]$ qemu-system-x86_64 --version
QEMU emulator version 7.0.0
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers

[nix-shell:~/gokrazy/virtual]$ gok vm run --arch=arm64                                                                                                                                                  
2025/01/28 18:58:23 building disk image
gokrazy gok g852031+ on GOARCH=amd64 GOOS=linux
[…]

[damdo]

Thanks for verifying! :)