gauntlet: init at 12

[schradert]

Closes #364534
Currently blocked by #282798

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 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
• Fits CONTRIBUTING.md.

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[schradert]

I also authored the working derivation upstream that this solution is based upon, which relies on tooling that can't be used in nixpkgs (i.e. crane). That helped me avoid an issue in this current PR: cargo vendoring in buildRustPackage fails with different sources of the same package. In developing the upstream implementation before switching to crane for other reasons, the solution in #282798 did work. However, as you can see in the code comments, the workarounds I attempted while awaiting these fixes were not successful.