tests.*: extend the existing config

[emilazy]

There can be load‐bearing things in config (e.g. forbidden licences, EULA agreements, and – in my case – a flag to silence a warning that would otherwise break CI). We should probably find a better solution for this kind of thing in general other than re‐importing Nixpkgs, but this fixes the immediate issue.

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

[jopejoe1]

An improvement to what we had before, in the long term, we should think of a different way than this. There is also some other stuff that gets lost when reimporting.