This requires a RUSTFLAG to be set before hand for rayon to build.
This brakes a lot of tools like rls and clippy by default and
require special configs for itnegration.
Additionally, rayon_futures is still 0.1 and not much work seem
to have gone into it. Ideally it should be replased with the tokio
runtime/threadpool.
Jordan Petridis
8fe1b70000