System information (version)

• OpenCV => 4.4
• Operating System / Platform => ubuntu 20
• Compiler => gcc 9.3

Detailed description

I'm trying to build opencv on a system without CUDA using -DWITH_CUDA=ON and -DBUILD_CUDA_STUBS=ONand using the extra modules from opencv_contrib. I'd expect to be able to build all of the cuda modules as stubs (similar to the behavior in opencv 2). Instead I get the following error:

opencv_contrib-4.4.0/modules/cudaarithm/src/lut.hpp:10:10: fatal error: cuda_runtime.h: No such file or directory
   10 | #include <cuda_runtime.h>
      |          ^~~~~~~~~~~~~~~~
compilation terminated.

Is this a bug, or am I misunderstanding the BUILD_CUDA_STUBS option?

Steps to reproduce

Build opencv from source using the above options.

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  answers.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc