elixir: use env shebang only on Darwin

[wh0]

The mix program from the elixir package has a long shebang:

#!/nix/store/b1wvkjx96i3s7wblz38ya0zr8i93zbc5-coreutils-9.5/bin/env /nix/store/mhm5dbd3lxhndrz5rcnl383jpp2k6xqq-elixir-1.17.3/bin/elixir

136 characters. Historical PR comments note that we include the env invocation even though we give an exact binary path because Darwin won't use another interpreted script as this program's interpreter.

I'm working on improving compatibility with older Linux kernels, which have a limit of 127 characters in the shebang command. This PR removes the env command other than in Darwin, which will bring us well under 127 characters.

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/) <- kind of, only mix
• 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.

---

Add a 👍 reaction to pull requests you find important.

[wh0]

GitHub Actions has encountered an internal error when running your job.

I guess I'll try flipping the draft mode on and off

[wh0]

Requesting reviews from code owners
This PR touches 1 files
File pkgs/development/interpreters/elixir/generic-builder.nix is unowned

possibly unrelated problem. but the file is beam-related.

@happysalada can you review?

[happysalada]

This looks good, but all the checks seem to be failing. Can you rebase on master to see if this is just a temporary error ?

[wh0]

oh staging has moved a little, so I maybe it'll be enough to rebase on that

[wh0]

thanks!