macOS High Sierra - ffmpeg to use nvidia eGPU - ERROR: failed checking for nvcc

I’m trying to get ffmpeg to use my external eGPU.
My hardware: macmini, 16 G ram, nvidia GeForce GTX960 in external housing, thunderbolt connection.

  • NVIDIA Web Driver 387.
  • CUDA Driver version 418.243

I’m trying to follow guide.
Alls seems good but when I run:

./configure --enable-cuda-sdk --enable-cuvid --enable-nvenc --enable-nonfree --enable-libnpp
--extra-cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64

I get stuck with
ERROR: failed checking for nvcc.

Search says my nvcc executable is to be found in /Developer/NVIDIA/CUDA-10.1/bin/nvcc
Permissions are as follows: -rwxr-xr-x@ 1 root wheel 259632 Aug 2 20:21 nvcc

I’ve tried running the samples and these seem to run fine.

Any pointer or help much appreciated!!