*: riscv fixes/changes

[Madouura]

Description of changes

Add support for the RISC-V StarFive VisionFive SoC.
Sections of this taken from https://github.com/zhaofengli/nixos-riscv64.

Current goal(s)

• Fix known upstream bugs in other issues/PRs

Past goal(s)

• Be able to build a basic NixOS system for riscv64-linux and have it run on VisionFive hardware

Past related issue(s)

• libcap (2.52 and above) does not compile on RISC-V. #168813
  • Fixed by libcap: fix cross-compilation support #168303
• logrotate fails to finalize on riscv64 build #168829
  • Fixed by nixos/logrotate: use packages from buildPackages in configuration che… #166992
• RISC-V linux cross compilation failing since staging-next merge #169278
  • Fixed by stdenv: use gcc11 for riscv #170991

Things done

• Built on platform(s)
  • x86_64-linux cross to riscv64-linux
  • aarch64-linux
  • riscv64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[Madouura]

The sd-image changes may be able to be genericized if multiple other systems also use a similar sdcard layout.

[Madouura]

Would have liked to use the starfive linux fork as a patch on top of our kernel instead, but it would always fail at the patch stage, so instead using it verbatim for now.

[colemickens]

cc: @zhaofengli

[Madouura]

...Now that I think about it, should probably be targeting staging as this is a HUGE rebuild for hydra lol.

[Madouura]

Should also mention I'm holding off on release notes until everything is properly building and I can test it on my hardware.
Currently, with an iso.nix (such as below) and nix-build nixos -A config.system.build.sdImage -I nixos-config=iso.nix at the nixpkgs root directory, it does build and generate an image (zst).

{ config, ... }:

{
  imports = [ "/home/mado/Documents/Development/nixpkgs/nixos/modules/installer/sd-card/sd-image-riscv64-visionfive-installer.nix" ];

  nixpkgs.crossSystem = {
    config = "riscv64-unknown-linux-gnu";
    system = "riscv64-linux";
  };
}

Edit: config.allowUnsupportedSystem = true; not needed.

[Madouura]

Moved mostly everything to NixOS/nixos-hardware#479

[Madouura]

Are we good for merge?

[SuperSandro2000]

@astro FYI

[Madouura]

Assuming the nlohmann_json change is okay, we should be good for merge.

[SuperSandro2000]

@ofborg build nix

Merging when nix still builds on the major platforms.