Add nix support

[nxy7]

Hi, I was interested in trying out roc-start but as I'm NixOS user I'd prefer to use flake over bash scripts.
I've added very crude buildRocPackage.nix file, flake and used that there.

As far as I know it might very well be the first thing doing something like buildRocPackage (I've browsed public roc repos and didn't find a single one distributing roc program as output of the flake).

I'm using roc-start distributed with this setup and it seems to be working
https://github.com/nxy7/dotfiles/blob/63efaa62e56125aed9d45555c5d088ac9f782f44/flake.nix#L87
https://github.com/nxy7/dotfiles/blob/63efaa62e56125aed9d45555c5d088ac9f782f44/home/packages.nix#L4

[nxy7]

If I'm getting Roc right dependencies will always be declared in main.roc and if any single one of them is updated/removed/added this hash should be updated.

[nxy7]

Actually it might need some small fix because the app is not getting arguments from the CLI (for some reason. I'll try to fix it soon, but you can tell me if you're interested in adding flake.nix to the repo.
EDIT. It seems like it might be some other issue not related to nix, as this happens even if I try to run it from CLI (not nix derivation)

[nxy7]

I've added printing of arguments passed in
https://github.com/nxy7/roc-start/blob/d67a6c1d84d62ec45463e733d387da61878eb850/src/main.roc#L43

For some reason arguments aren't parsed at all, doesn't seem to be nix issue at all..

[imclerran]

Thanks for working on Nix support. What you are running into is #68 which actually is roc-lang/basic-cli#82, which causes cli args to be empty. This is an issue when using the legacy linker.

The filer for #68 tried using the surgical linker, which does not have the basic-cli args issue, but the surgical linker did not work in his case.

Have you tried building with --linker=surgical? I know the surgical linker still has issues on Linux, but I believe that varies by distro.

[nxy7]

Surgical linker also doesn't seem to be working. I've actually refactored buildRocPackage out from this PR and will try to get it into main Roc repo. Once new release fixes issues with the linker I'll open this PR and ping you.