vtk: enable qt gui support

[matthuszagh]

Motivation for this change

Part of this PR. @jonringer

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.

[bcdarwin]

nixpkgs-review succeeds, but lib/libvtkGUISupportQt-8.2.so.1 is already present in the output of vtkWithQt5 on master (more generally the results of find result -name '*GUI*' are identical), so it seems like this option is already implied by VTK_Group_Qt in the current version of VTK?

[matthuszagh]

@bcdarwin thanks for the review and it seems you're right. Thanks for spotting that. I had originally written this PR for an earlier version of the derivation that didn't provide the Qt GUI support. Closing this.

[bcdarwin]

[Probably obviated by #84772.]