Bitwig needs JACK to be able to play any sound. It'll try to link to it only after you've opened a project, which might be why this slipped through. Either way, I've added libjack2 as a runtime dependency, so now it works fine.

Motivation for this change

The current bitwig-studio3 runs, but cannot dynamically link at runtime to libjack2, so it can't use any sound.

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.