Some problem with CMake when importing the project to CLion

I use CLion with WSL to import Clang’s CMake project, but it gives an error while generating the project configuration as shown by the first image. And the code at the error place is as the second image. It’s a function defined in llvm/cmake/modules/AddLLVM.cmake. I don’t know why this happened because it seems that in clang/CMakeLists.txt the module “AddLLVM” has been included as the third image. I’m not familiar with CMake and thanks for any help.