Slow Rust install on Windows

[Jake-Shadle]

In some CI environments such as Travis etc, installing rustup can take an incredibly long time on Windows due mainly to the installation of documentation.

• rust-lang: Making docs optional again #998

[repi]

This is not that much of a problem on our new Buildkite Windows CI right @Jake-Shadle as we have it pre-installed there?

So although this is something we would want to be improved in Rust it in that case is not that important for us anymore so could close it?

[Jake-Shadle]

Yes, very true!