Just here to say we really need to allow hooks to disable installing rust-doc on Windows for CI builds. As it stands, Windows builds on CI take ~5⨉ longer than Linux or macOS just to get through the setup step, because NTFS kind of chokes when dealing with a large number of small files. 
(This is something I am painfully familiar with from working with Ember CLI in my day job.) I’m happy to pitch in on what’s needed to make that happen if someone points me in the right direction.