QDoc libclang requries an updated MSVC 2019 Version

While working at upgrading LLVM/Clang to version 10.0.0 the VM that builds for Visual Studio 2019 failed with this error:

CMake Error at cmake/modules/CheckCompilerVersion.cmake:62 (message):
  Host Visual Studio version 16.4 is known to miscompile part of LLVM, please
  use clang-cl or upgrade to 16.5 or above (use
  -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON to ignore) 

For the moment I will try adding -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON to the build script. But this should be removed when MSVC2019 version gets updated.