Merge ref 'fd2eb391d032' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: fd2eb391d032181459773f3498c17b198513e0d0
Filtered ref: 0d1dff7

This merge was created using https://github.com/rust-lang/josh-sync.

Author: The rustc-josh-sync Cronjob Bot

compiler-builtins/Cargo.toml

@@ -19,6 +19,8 @@ links = "compiler-rt"
 bench = false
 doctest = false
 test = false
+# make sure this crate isn't included in public standard library docs
+doc = false
 
 [dependencies]
 core = { path = "../../core", optional = true }