RFC: Add a target for building a Cargo binary

[UebelAndre]

I've come across a desire to be able to use cargo to perform some simple operations.

Namely:

• Generate metadata (for Added rule_cbindgen #392)
• Publish crates to a registry (Feature Request: Add a rule for publishing to a crate registry #458)

I've seen concerns about the use of Cargo within these rules but I do feel like being able to use it in sandboxes, deterministic ways would be beneficial for the rules. I understand this can be a slippery slope so if a target were to be added it it should be understood that it's to be used extremely selectively.

My hope for right now is to open a PR that adds an aspect for generating cargo metadata. This is probably required for #392 but could also have wider benefits.

Very interested in hearing more thoughts. 🙏

[UebelAndre]

Oh man, I didn't even know #413 was a thing.

[UebelAndre]

Well then I feel like this is way less controversial. I may make a PR for this soon.

[UebelAndre]

Gonna close this, I didn't realize cargo binaries could be found in the rust_toolchain toolchains. I think this binary should have it's own toolchain, which is something pointed out in #523

That should be the tracking issue for doing that.