Feature request: Allow the VMAF CUDA back-end to be built via clang and LLVM as an alternative to the full CUDA SDK.

[Brainiarc7]

Subject matter refers.
A build derived with standard clang and llvm tooling would also ease up licensing integrations in projects such as FFmpeg, where the accompanying filter libvmaf_cuda is built under a non-free licensing model, requiring the proprietary CUDA SDK.
As it stands, there are multiple build and runtime issues encountered with this dependency on the CUDA SDK. Also see #1220

Please review and revert on the same.

[gedoensmax]

The SDK is just required from compilation and not for distribution. For distribution only the driver library is required. I am not a licensing expert by any means, but does that stand as a problem ?
Otherwise your contribution and guidance is very welcome ! I would also love to load the driver lib via dlopen so that a default compile can be with cuda enabled.

[kylophone]

I would also love to load the driver lib via dlopen so that a default compile can be with cuda enabled.

Would ffnvcodec help here?: https://github.com/FFmpeg/nv-codec-headers/blob/master/include/ffnvcodec/dynlink_cuda.h

[gedoensmax]

It would, it's more of a prioritisation issue i would say.