That C++20 header is already conditionally included bu `<CGAL/config.h>`. See https://github.com/lrineau/cgal/blob/e6b4d83cff944772ea5ed67bc414b61547d86432/Installation/include/CGAL/config.h#L322
That C++20 header is already conditionally included bu `<CGAL/config.h>`. See https://github.com/lrineau/cgal/blob/e6b4d83cff944772ea5ed67bc414b61547d86432/Installation/include/CGAL/config.h#L322