I recently heard a google employee come speak at my university about how google's main codebase is compiled using clang, and their janitorial work is done using clang mapreduce [1]. Furthermore, that google employee talked about how google is working with the LLVM team to integrate the toolchain into visual studio for cross-platform compilation [2]. Pretty cool stuff!
[1] (similar talk) https://www.youtube.com/watch?v=mVbDzTM21BQ