[CMake] try creating symlink first on windows

//-E create_symlink//  is available on windows since CMake 3.13 (LLVM now uses 3.13.4)
It may needs administrator privileges or enabled developer mode (Windows 10)
See https://cmake.org/cmake/help/latest/release/3.13.html

Reviewed By: kbobyrev

Differential Revision: https://reviews.llvm.org/D99170