Error message in build.nu script is not printed out.

[thiskappaisgrey]

Hi,
Right now, if I do a nix build .#error derivation, the error message of that derivation is swallowed because of these lines: https://github.com/DeterminateSystems/nuenv/blob/main/nuenv/builder.nu#L141

Not having the error message from error.nu is not very helpful to me... Maybe the intention is to use nix shell .#error and see the error messages there and those lines were intentional but I think it'd still be helpful to get nushell error messages in a nix build. Anyways, if I comment those lines (that exists the program) - the script still exits (doesn't continue running the other phrases) but the error messages from nuenv are shown:

I made a branch on my fork here: https://github.com/thiskappaisgrey/nuenv/blob/prop-error-msg-in-builder/nuenv/builder.nu#L137

Since I wasn't sure what the intention was for error handling, I didn't make a PR, but I can at a later date.