cmake DEAL_II_COMPILER_HAS_ATTRIBUTE_FUNC examples

dealii/dealii cmake/checks/check_02_compiler_features.cmake :222 

CHECK_CXX_SOURCE_COMPILES(
    "
    #include <iostream>
    int main()
    {
      std::cout << __func__ << std::endl;
      return 0;
    }
    "
    DEAL_II_COMPILER_HAS_ATTRIBUTE_FUNC)