message: pybind11 extension code should be compiled with hidden visibility
diff: @@ -268,6 +268,7 @@ if(BUILD_ONNX_PYTHON)
  add_library(onnx_cpp2py_export MODULE "${ONNX_ROOT}/onnx/cpp2py_export.cc")
  set_target_properties(onnx_cpp2py_export PROPERTIES PREFIX "")
  + set_target_properties(onnx_cpp2py_export PROPERTIES COMPILE_FLAGS "-fvisibility=hidden")
  set_target_properties(onnx_cpp2py_export PROPERTIES SUFFIX ${PY_EXT_SUFFIX})
  set_target_properties(onnx_cpp2py_export PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
  target_include_directories(onnx_cpp2py_export PRIVATE "${ONNX_ROOT}" "${CMAKE_CURRENT_BINARY_DIR}" "${PROTOBUF_INCLUDE_DIRS}" "${PYTHON_INCLUDE_DIR}")
  