nixos/activation-script: Fix dependencies for dry activation

[dasJ]

Motivation for this change

#136605 broke tools like agenix.
The comment in the code should pretty much explain why this fixes it.
For the simple test, this results in:

$ grep '#### Activation script snippet' dry-activate
#### Activation script snippet specialfs does not support dry activation.
#### Activation script snippet binfmt does not support dry activation.
#### Activation script snippet stdio does not support dry activation.
#### Activation script snippet binsh does not support dry activation.
#### Activation script snippet domain does not support dry activation.
#### Activation script snippet users:
#### Activation script snippet groups does not support dry activation.
#### Activation script snippet etc does not support dry activation.
#### Activation script snippet hostname does not support dry activation.
#### Activation script snippet modprobe does not support dry activation.
#### Activation script snippet nix does not support dry activation.
#### Activation script snippet udevd does not support dry activation.
#### Activation script snippet usrbinenv does not support dry activation.
#### Activation script snippet var does not support dry activation.
#### Activation script snippet wrappers does not support dry activation.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• 21.11 Release Notes (or backporting 21.05 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.

[ryantm]

I think this is a good solution, @dasJ! The only possible issue I see is if some dry activation script has a dependency that doesn't support dry activation, but the dry-activation script depends critically on the dependency running, which seems unlikely to me.

[dasJ]

I don't think this is a relevant problem because when you get to dry-running anything you have already booted your system, hence all Activation Scripts were already run in non-dry mode. This means all things that I can think of (like setting the hostname, loading kernel modules, …) should have already been run at the point you get get the chance to do a dry activation

[dasJ]

@ryantm You should be able to remove your workaround: https://nixpk.gs/pr-tracker.html?pr=137508