Motivation for this change

Using fetchFromGitHub and version/rev, so future releases can be picked by bot.

Of the grid, I tried to compile dev branch of Qt5 with minor success. GStreamer plugins was not picked-up by the player. And anyway it is to early to make clementine-qt5, since it is just a small side branch upstream today.

If someone has additional suggestions, I would like to get input.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• 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 nox --run "nox-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)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.