cpu support?

Hi, I am trying to install your amazing software on my mac without nvidia gpu, bnn does not build since it tries to find cuda:

CMake Error at /usr/local/Cellar/cmake/3.10.2/share/cmake/Modules/FindCUDA.cmake:682 (message):
Specify CUDA_TOOLKIT_ROOT_DIR
Call Stack (most recent call first):
CMakeLists.txt:10 (FIND_PACKAGE)

The CMakeLists.txt at line 10 calls FIND_PACKAGE for CUDA. Examine the CMake configuration to understand the build dependencies and conditional logic for GPU support. Look for existing CPU build options or flags in the project. The goal is to modify the build to work without CUDA, likely by adjusting CMakeLists.txt and related build scripts.

索引モデルが issue の本文から書いたものです。