Motivation for this change

Run NixOS on the Raspberry Pi 4B #63720.

This pull request has breaking changes that need feedback!

Changes Mage:

• Bumped WiFi and boot firmware for the raspberry pi.
• Updated the default raspberry pi bootloader to work with the rpi4.
• Bumped the kernel. This encountered an interesting issue: The raspberry pi currently has a single kernel image: linux_rpi, which uses different defconfig settings depending on architecture. The rpi4 has the same architecture as the rpi3, but should use a different defconfig setting. I cannot see how to modify the current kernel package backwards-compatibly to do this. As a result, I've split it into several. Feedback on this would be good. It will break any existing builds using this kernel.

Outstanding issues:

• Uboot support is not available upstream, as far as I can tell.
• The raspberry pi sdcard build is broken, both due to the lack of uboot, and because the issue of selecting the correct kernel.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Notify maintainers

cc @