Fix C++17 targets in cmake.
Fix C++17 targets in cmake.

CMake doesn't recognize CUDA_STANDARD=17 until v3.18, and the
CUDA_STANDARD_REQUIRED property doesn't seem to work properly. See
CMake bug: https://gitlab.kitware.com/cmake/cmake/-/issues/20953

To allow the C++17 configs to actually use C++17, we need to bump our
minimum CMake version to 3.18.

NVlabs/CUB,NVIDIA/cub,NVlabs/cub