message: Let the post-processing hook also handle pb.cc file
diff: @@ -200,6 +200,7 @@ function(RELATIVE_PROTOBUF_GENERATE_CPP NAME SRCS HDRS ROOT_DIR DEPEND)
  COMMAND ${ONNX_PROTOC_EXECUTABLE}
  ARGS ${PROTOC_ARGS}
  COMMAND "${CMAKE_COMMAND}" -DFILENAME=${OUTPUT_PB_HEADER} -DNAMESPACES=${ONNX_NAMESPACE} -P ${ONNX_PROTO_POST_BUILD_SCRIPT}
  + COMMAND "${CMAKE_COMMAND}" -DFILENAME=${OUTPUT_PB_SRC} -DNAMESPACES=${ONNX_NAMESPACE} -P ${ONNX_PROTO_POST_BUILD_SCRIPT}
  DEPENDS ${GENERATED_PROTO} ${DEPEND}
  COMMENT "Running C++ protocol buffer compiler on ${GENERATED_PROTO}"
  VERBATIM )
  