Motivation for this change

Adds an --export flag to make-wrapper.sh to export previously unexported variables. This is important because the wrapped program is called using exec, so any unexported variables will not be visible to the wrapped program.

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/)
• Fits CONTRIBUTING.md.

I'm having trouble testing this locally because it triggers a TON of rebuilds.