stdenvBootstrapTools: in darwin, only run install_name_tool on Mach-O files

[tjni]

Description of changes

The Darwin stdenv rework (#240433) switches as to be the Clang assembler, but it is wrapped in a shell script. We need to update the Darwin bootstrap test to skip running install_name_tool on it, since it fails when given a file that is not a Mach-O binary. The tests seem to pass regardless.

I'm not sure I should be (or can) use the file command for this purpose. Open to feedback on how to make this better.

Relevant for staging-next: #241951

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, 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[NickCao]

We have an isMachO helper in stdenv.

nixpkgs/pkgs/stdenv/generic/setup.sh

Line 339 in 974afd4

isMachO() {

[tjni]

Wow, that's a cool function. Thank you, @NickCao.