The official LLVM 4.0 build for Windows integrates with Visual Studio up to Visual Studio 2015. Unfortunately it still doesn\'t support Visual Studio 2017.
It requires some msbuild targets that only ship with the C++ v140 toolset, and VS 2017 only installs the v141 toolset by default. If you open the VS 2017 installer, find the checkbox for the v140 toolset and install that then the right C++ msbuild targets will be available and the thing will work.