perl: substitute /bin/pwd with host pwd

[illegalprime]

Motivation for this change

/bin/pwd is replaced during the build with nix's version.
it was incorrectly set to the build-time pwd, this would set it to the host's pwd

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[benley]

This definitely looks like a good fix but I'm not 100% sure if it's safe to merge; maybe it had something to do with perl being a bootstrapping dependency? @edolstra introduced this quirk so perhaps he should take a look.

[illegalprime]

btw: should I be putting PRs into staging? (not master)

[benley]

Master is fine for most things; staging is for changes that are going to require massive rebuilds, as it gives hydra a chance to catch up before things hit the nixos channels. Perl may actually be one of those things :-P

btw, here is a comment I found about the $pwd thing in git blame history:

    # There's an annoying bug on sandboxed Darwin in Perl's Cwd.pm where it looks for pwd
    # in /bin/pwd and /usr/bin/pwd and then falls back on just "pwd" if it can't get them
    # while at the same time erasing the PATH environment variable so it unconditionally
    # fails. The code in question is guarded by a check for Mac OS, but the patch below
    # doesn't have any runtime effect on other platforms.
    postPatch = optional stdenv.isDarwin ''
      pwd="$(type -P pwd)"
      substituteInPlace dist/PathTools/Cwd.pm \
        --replace "/bin/pwd" "$pwd"
    '';

someone else should approve this, I think

[illegalprime]

yeah, :( the motivation here is to not bring along build-time dependencies when cross compiling

[illegalprime]

I'm not sure why ofborg isn't building, it's building on my machine... will investigate more

[Ekleog]

@GrahamcOfBorg eval

@GrahamcOfBorg build perl gitFull

[Ekleog]

@illegalprime This change appears to break evaluation on at least darwin: https://github.com/NixOS/nixpkgs/pull/58979/checks?check_run_id=135801652

[lopsided98]

See #65761 for my PR that fixes the Darwin issue and another accidental reference.

[illegalprime]

closing in favor of #65761