nightly_linux_clang_libcxx build broken. Failures during linking opencv in intra_process_demo

[j-rivero]

Bug report

Required Info:

• Operating System:
  • Ubuntu Focal (docker container)
• Installation type:
  • from source
• Version or commit hash:
  • 7b736b0

Steps to reproduce issue

See job https://ci.ros2.org/view/nightly/job/nightly_linux_clang_libcxx/ (i.e: https://ci.ros2.org/view/nightly/job/nightly_linux_clang_libcxx/375/)

Expected behavior

To compile.

Actual behavior

Failing to compile due to problems with the linking of opencv4:

08:14:26 [19.061s] [ 28%] Linking CXX executable image_pipeline_with_two_image_view
08:14:26 [20.861s] /usr/bin/ld: CMakeFiles/image_pipeline_with_two_image_view.dir/src/image_pipeline/image_pipeline_with_two_image_view.cpp.o: in function `draw_on_image(cv::Mat&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int)':
08:14:26 [20.861s] /home/jenkins-agent/workspace/nightly_linux_clang_libcxx/ws/src/ros2/demos/intra_process_demo/include/image_pipeline/common.hpp:79: undefined reference to `cv::putText(cv::_InputOutputArray const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, cv::Point_<int>, int, double, cv::Scalar_<double>, int, int, bool)'
08:14:26 [20.873s] /usr/bin/ld: CMakeFiles/image_pipeline_with_two_image_view.dir/src/image_pipeline/image_pipeline_with_two_image_view.cpp.o: in function `Mat':
08:14:26 [20.873s] /usr/include/opencv4/opencv2/core/mat.inl.hpp:548: undefined reference to `cv::error(int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*, char const*, int)'
08:14:26 [20.874s] /usr/bin/ld: /usr/include/opencv4/opencv2/core/mat.inl.hpp:561: undefined reference to `cv::error(int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*, char const*, int)'
08:14:26 [20.881s] /usr/bin/ld: CMakeFiles/image_pipeline_with_two_image_view.dir/src/image_pipeline/image_pipeline_with_two_image_view.cpp.o: in function `operator()':
08:14:26 [20.881s] /home/jenkins-agent/workspace/nightly_linux_clang_libcxx/ws/src/ros2/demos/intra_process_demo/include/image_pipeline/image_view_node.hpp:54: undefined reference to `cv::imshow(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, cv::_InputArray const&)'

Additional information

Problem does not exist un my local amd64 Ubuntu Bionic system using opencv 3.2.0 and clang 6.0.0.