Nix doesn't work on Windows

[domenkozar]

Given stack.yaml:

...
nix:
  enable: true
...

The project can't be build on Windows, since stack will try to use Nix also there. While it's possible to use Nix via cygwin or WSL, that's rarely done.

I suggest we disable Nix on Windows (and optionally support forcing it if really wanted).

[mgsloan]

I hear that nix on wsl can work - https://www.tweag.io/posts/2017-11-10-nix-on-wsl.html - though noidea if that would work with stack.

IMHO it'd make sense to just not have enable: true. There are a few other stack.yaml options that allow you to break builds for users with configurations different than yours, for example, extra-lib-dirs. Not saying this is ideal, but it's the way things are, currently. Definitely some interesting tradeoffs between configurability and universality.

[domenkozar]

@mgsloan we do default to false currently, but that trips people since they forget to pass --nix and stack doesn't warn about it. Results into very obscure errors. I'd like to make default configuration sane by enabling Nix, but Windows prevents that.

[mgsloan]

I see! This is another potential usecase for #3369

[mgsloan]

I've opened a PR, #3833 which always overrides with enable: false on windows.

Previously when I suggested that #3369 be implemented for this, I didn't properly consider that when using WSL it will be built as an ELF binary that thinks it's targeting linux.