Make binary releases of Cargo

[brson]

To pair Cargo releases with Rust our distribution servers must have versioned releases of Cargo to download. Add new stable dist builders and modify the Rust release process to also do a Cargo release.

re https://internals.rust-lang.org/t/perfecting-rust-packaging-the-plan/2767

[Ericson2314]

What's the status of this? https://static.rust-lang.org/cargo-dist/index.html was a thing? Now we have actual channels?

[Ericson2314]

I see #2968 (comment) but that doesn't help get nightlies by date.

[Ericson2314]

@flosse informed me https://static.rust-lang.org/dist/index.html now contains Cargo too. All is well!

[carols10cents]

Sounds like this can be closed now. Please reopen if I'm mistaken!