nixos/installation-device: don’t include stdenv

[emilazy]

A basic NixOS system shouldn’t require stdenv to install, and it adds something like 45 MiB of build tools to the installer closure. This doesn’t really help much at present since WebKitGTK(?!) has a dodgy reference to GCC, but it’s a step in the right direction.

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/)
• Nixpkgs 25.11 Release Notes (or backporting 24.11 and 25.05 Nixpkgs Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
• NixOS 25.11 Release Notes (or backporting 24.11 and 25.05 NixOS Release notes)
  • (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, pkgs/README.md, maintainers/README.md and other contributing documentation in corresponding paths.

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[vcunat]

Unless I made some mistake, I see the ISO size decrease by 5 MiB just by this PR. (I assumed that some other parts still pulled almost all of it.)

[emilazy]

It’s probably the WebKitGTK pulling in GCC thing. That should be fixed and then this should be something like a ~45 MiB uncompressed win I think.

[vcunat]

Yes, it does pull it. And maybe other things. I also saw really lots of -dev packages on the ISO yesterday.

[emilazy]

#418819 should make this a bigger win. Apparently it’s some ~80 MiB compressed savings to drop stdenv from the minimal ISO even without it. stdenv is currently required for NixOS installations, though (but it’s easy to move those cases to stdenvNoCC and offline installs aren’t currently possible yet anyway, so I don’t think it needs to block this).

[vcunat]

Installer tests need fixing, e.g. nixosTests.installer.simpleUefiSystemdBoot, most likely simply by adding stdenv into extra inputs (don't recall where exactly off the top of my head).

[emilazy]

Should be fixed now. Haven’t measured the size difference now that GCC is out of the closure.

[vcunat]

79 MiB for the minimal ISO size.