I have resolved the original issue. I added a symbolic link /usr/local/cuda to point to /usr/local/cuda-9.0. It seems one of the find scripts is still using /usr/local/cuda despite setting CUDA_TOOLKIT_ROOT_DIR to /usr/local/cuda-9.0
Now the cmake scripts correctly find CUDA. However the build fails with:
/home/developer/NVIDIA/Drive/5050bL_SDK/DriveSDK/toolchains/tegra-4.9-nv/usr/bin/aarch64-gnu-linux/…/…/libexec/aarch64-gnu-linux/gcc/aarch64-gnu-linux/4.9.2/ld: skipping incompatible /usr/local/cuda/lib64/libcudart.so when searching for -lcudart
I believe this is because the CUDA 9.0 cross compile package is not installed. Where can I find the appropriate .deb?