Here I think we just want:

```
        option(DYND_CUDA
             "Build a libdynd library with CUDA"
             OFF) # While CUDA support is in development, we default to OFF.
```

without the `if(CUDA_FOUND)` part, and later if we change that we can change it to

```
        option(DYND_CUDA
             "Build a libdynd library with CUDA"
             CUDA_FOUND) # Enable CUDA by default if it was found
```