Rust version support

[Alexis-Bize]

Is your feature request related to a problem? Please describe. Can not use the nightly version of Rust with [email protected].

Describe the solution you'd like Allow version override via process.env.RUST_VERSION or an alternative.

Describe alternatives you've considered Using builds instead of functions in now / vercel JSON file.

Additional context downloadRustToolchain (see https://github.com/mike-engel/now-rust/blob/master/src/install-rust.ts#L4) supports a version argument, but isn't / can not be used.

Thank you!

[mike-engel]

This looks like a regression that's been around for a while, probably when they switched config formats for runtimes. I'm happy to support a RUST_VERSION variable, but can't promise much time soon to work on it. If you'd like to submit a PR, I'm happy to review it and merge it.

[Alexis-Bize]

No worries, I'll try to take a look then 👌Thank you!