Pauze C++ Indexing when starting a build

Clangrefactoringbackend seems to take muuuch CPU and takes a long time to complete. So I think it's not needed to let it run full throttle when you start a build of your code, because at that moment, you want your build to happen fast, and not let it be slowed down by C++ Indexing which you are not using anyway at that moment because you are done with your code changes. This should be an easy speed improvement for the end user I think.