Fix the bootloader hanging during uefi exit_boot_services

[Wasabi375]

Fixes #400

Switch from using the "-bios" flag to using "-pflash" instead. Using "-bios" is not recomended see: https://lists.katacontainers.io/pipermail/kata-dev/2021-January/001650.html

This also allows us to easily update the ovmf-prebuild binaries.

This fixes https://github.com/rust-osdev/bootloader/issues/400. I'm not sure whether the issue was an outdated ovmf version or the bios-pflash change. I can't tell what version is published with the ovmf-prebuild crate, so I can't check.

Ovmf binaries are no longer provided by the ovmf-prebuild crate. Instead we now download them from the ovmf-prebuild github releases of the same crate. Unlike the crate, those are actually updated.

[Wasabi375]

The test/runner/src/ovmf.rs file is based on https://github.com/rust-osdev/uefi-rs/blob/ac19526656953c32e8e0ef7bc703f7700b151ae4/xtask/src/qemu.rs#L65

I am 99% certain that this fixes the issue in #400. However I want to implement the same fix in my own kernel to make sure.

I also still need to update https://github.com/rust-osdev/bootloader/blob/main/docs/create-disk-image.md

[Wasabi375]

Ok, I can confirm that using pflash works on my machine. I don't really understand why the CI tests fails. Maybe someone else can try this fix on their machine and give me feedback. The CI log is not really helpful.

[Wasabi375]

I wonder if we should provide most of the code in test/runner/src/ovmf.rs as a library. Maybe as an updated version of ovmf-prebuild. Otherwise this is a lot of code that needs to be copied into any project using the bootloader.

[Wasabi375]

Do you know how I can get the actual logs from qemu in the CI ? Right now the tests time after 30 minutes but I can't reproduce this locally.