Merge from rustc

Author: Kobzol

library/compiler-builtins/README.md

@@ -25,3 +25,5 @@ More details are in [LICENSE.txt](LICENSE.txt) and
 
 [MIT License]: https://opensource.org/license/mit
 [Apache License, Version 2.0]: htps://www.apache.org/licenses/LICENSE-2.0
+
+WIP