git: support cross-compilation by disabling perl support

[Mindavi]

Motivation for this change

Support cross-compilation. This reduces functionality (honestly, I don't know which parts require perl support), but will at least make git compile successfully. Otherwise you don't have git at all.

See also #66741

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.

[primeos]

I've verified that this fixes the cross-compilation and disabling the Perl support in that case good to me (IIRC Perl is mainly required for interactive scripts like git add -{i,p} and some porcelain commands like git-blame and git-send-email - but the essential stuff should work without Perl and upstream is currently rewriting (all?) Perl scripts in C).

Note: This breaks instantiating pkgsCross.aarch64-multiplatform.gitFull but that is to be expected and given that gitFull likely won't cross-compile it seems better if this fails early.