haskellPackages.hnix: Patch to fix broken location annotations

[expipiplus1]

Also reenable tests for update-nix-fetchgit

Motivation for this change

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/)
• Added a release notes entry if the change is major or breaking
• Fits CONTRIBUTING.md.

[cdepillabout]

@ofborg build haskellPackages.update-nix-fetchgit update-nix-fetchgit haskellPackages.hnix

[sternenseemann]

@ofborg build haskellPackages.yarn2nix

[cdepillabout]

Looks like everything is building on x86_64-linux at least, thanks!