Add toolchain support for rules_cue

[folliehiyuki]

Is your feature request related to a problem? Please describe.

It would be nice to have rules_cue use cue package from Nixpkgs.

Describe the solution you'd like

Exposing nixpkgs_cue_configure rule. For bzlmod users, maybe also have additional rules_nixpkgs_cue module.

Describe alternatives you've considered

None.

Additional context

rules_cue doesn't have any usage documentation at the moment, so here is a snippet how CUE is enabled:

bazel_dep(name = "rules_cue", version = "0.4.2")

cue = use_extension("@rules_cue//cue:extensions.bzl", "cue")
cue.download(version = "v0.6.0")

The implementation for the toolchain is here: https://github.com/seh/rules_cue/blob/main/cue/private/tools/cue/toolchain.bzl

[benradf]

Thanks for the feature request @folliehiyuki. Supporting more languages and toolchains in rules_nixpkgs is something we're interested in, though I'm not sure when we'll get around to prioritising this work. In the meantime, if you'd like to take this on and submit a pull request, let me know and we can discuss.