message: Include `omp` headers on macOS
diff: @@ -252,6 +252,11 @@ if (MFEM_USE_OPENMP OR MFEM_USE_LEGACY_OPENMP)
  endif()
  find_package(OpenMP REQUIRED)
  set(OPENMP_LIBRARIES ${OpenMP_CXX_LIBRARIES})
  + if(APPLE)
  + # On macOS, the compiler needs additional help to find the <omp.h> header.
  + # See issue #2642 for more information.
  + include_directories(${OpenMP_CXX_INCLUDE_DIRS})
  + endif(APPLE)
  endif()
  # SuiteSparse (before SUNDIALS which may depend on KLU)
  