Docker build failed: Could not find OpenMP_CXX

[markuspi]

I tried building using Docker and ran into this CMake error:

CMake Error at /usr/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find OpenMP_CXX (missing: OpenMP_CXX_FLAGS OpenMP_CXX_LIB_NAMES)
Call Stack (most recent call first):
  /usr/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.24/Modules/FindOpenMP.cmake:547 (find_package_handle_standard_args)
  CMakeLists.txt:58 (find_package)

It looks like this is due to a missing dependency libomp-X-dev where X is the major version of clang++. In my case for Ubuntu 20.04 and the newest clang apt repository, adding apt install -y libomp-16-dev fixed the problem