Found this explication for Cuda Toolkit 8 isn't working with Xcode 8 on Sierra
Xcode 8 is not currently supported with the CUDA Toolkit 8 compiler for Mac. We are working on providing an update shortly. Until then, the developers should use Xcode 7.x with the CUDA Toolkit 8 for compiling their code on Mac macOS 10.12. Alternatively, they can run applications compiled with older versions of CUDA Toolkit and Mac/Xcode on Mac macOS 10.12.