message: Minimally fix CMakeLists on Windows
  Thank you!
diff: @@ -109,12 +109,14 @@ function(RELATIVE_PROTOBUF_GENERATE_CPP SRCS HDRS ROOT_DIR)
  list(APPEND ${SRCS} "${OUTPUT_PB_SRC}")
  list(APPEND ${HDRS} "${OUTPUT_PB_HEADER}")
  + if(NOT EXISTS "${OUTPUT_PROTO_DIR}")
  + file(MAKE_DIRECTORY "${OUTPUT_PROTO_DIR}")
  + endif()
  +
  add_custom_command(
  OUTPUT "${GENERATED_PROTO}"
  - COMMAND mkdir
  - ARGS -p ${OUTPUT_PROTO_DIR}
  - COMMAND ${PYTHON_EXE} ${GEN_PROTO_PY}
  - ARGS -p ${ONNX_NAMESPACE} -o ${OUTPUT_PROTO_DIR} ${FILE_WE}
  + COMMAND "${PYTHON_EXE}" "${GEN_PROTO_PY}"
  + ARGS -p "${ONNX_NAMESPACE}" -o "${OUTPUT_PROTO_DIR}" "${FILE_WE}"
  DEPENDS ${INFILE}
  COMMENT "Running gen_proto.py on ${INFILE}"
  VERBATIM )
  