Motivation for this change

IGV 2.4.6 is the latest stable IGV release. Branch 2.4.x brings in notable features, including CRAM and 10x support.

JRE 8 is required, but that's the default in Nixpkgs, so no changes to the derivation are needed.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-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/)
• Fits CONTRIBUTING.md.

@mimadrid @infinisil