The perl reference is in the interpreter line for c_rehash, so fix
that while we're here.

Motivation for this change

I initially ported perl-cross to darwin for aarch64-darwin bootstrap tools in #105026, but it wasn't of high enough quality to upstream. Looking at the dependency for perl, it was only from openssl, and not from any part used by the bootstrap tools.

It seems to be only the interpreter line for c_rehash, which is currently inconsistent.

Before

Native:
1.0.2: #!/nix/store/76qi9w2yd4xb8kykw3maj7n5g35qk7k2-perl-5.32.1/bin/perl
1.1: #!/usr/bin/env perl

Cross:
1.0.2: #!/nix/store/2gcqvw532bvcf4rvvg7a2rhpcyhxm28j-perl-5.32.1-aarch64-unknown-linux-gnu/bin/perl
1.1: #!/usr/bin/env perl

After

Native:
1.0.2: #!/nix/store/76qi9w2yd4xb8kykw3maj7n5g35qk7k2-perl-5.32.1/bin/perl
1.1: #!/nix/store/76qi9w2yd4xb8kykw3maj7n5g35qk7k2-perl-5.32.1/bin/perl

Cross:
1.0.2: #!/nix/store/2gcqvw532bvcf4rvvg7a2rhpcyhxm28j-perl-5.32.1-aarch64-unknown-linux-gnu/bin/perl
1.1: #!/nix/store/2gcqvw532bvcf4rvvg7a2rhpcyhxm28j-perl-5.32.1-aarch64-unknown-linux-gnu/bin/perl

Cross without perl:
1.0.2: #!/usr/bin/env perl
1.1: #!/usr/bin/env perl

let
  native = import ./. {
    localSystem = "x86_64-linux";
  };

  cross = import ./. {
    localSystem = "x86_64-linux";
    crossSystem = "aarch64-linux";
  };
in native.runCommand "openssl-interpreters" {} ''
  report() {
    local version=$1
    local pkg=$2
    echo -n "$version: "
    head -1 $pkg/bin/c_rehash
  }
  (
    echo "Native:"
    report 1.0.2 ${native.openssl_1_0_2}
    report 1.1   ${native.openssl_1_1}
    echo

    echo "Cross:"
    report 1.0.2 ${cross.openssl_1_0_2}
    report 1.1   ${cross.openssl_1_1}
    echo

    echo "Cross without perl:"
    report 1.0.2 ${cross.openssl_1_0_2.override { withPerl = false; }}
    report 1.1   ${cross.openssl_1_1.override { withPerl = false; }}
  ) > $out
''

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• 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 nixpkgs-review --run "nixpkgs-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)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.