MSBuild integration: get the LibraryPath right (PR18707)

It was pointing to lib\clang\3.4, but now we're on 3.5.
Make CMake insert the right version automatically.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201363 91177308-0d34-0410-b5e6-96231b3b80d8