Option 1 will take a long time. Writing a libc takes a long time, and transitioning the whole of Google codebase to a new libc takes even longer to iron out all of the incompatibilities.
If one goes with option 2, he/she may have many more achievements to write on his/her promotion packet during the time he/she would have spent implementing a new libc. So I hardly think promotion is the incentive here.
If one goes with option 2, he/she may have many more achievements to write on his/her promotion packet during the time he/she would have spent implementing a new libc. So I hardly think promotion is the incentive here.