Motivation for this change

Currently, using callCabal2nix requires all the build-time dependencies of cabal2nix. pkgs.cabal2nix uses justStaticExecutables. So if it is cached, then you only need to download these executables, not all the unnecessary library dependencies.

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.