Failure of MSVC build on Appveyor

[msakai]

MSVC build on Appveyor fails with the following error: https://ci.appveyor.com/project/pfnet-research/menoh/builds/34608060/job/awhcqncaxowfypvm

  onnx_menoh_onnx.pb.cc
  onnx-operators_menoh_onnx.pb.cc
C:\protobuf-3.6.0-msvc\include\google/protobuf/stubs/logging.h(100): error C2220: warning treated as error - no 'object' file generated (compiling source file C:\projects\menoh\build\external\onnx\onnx\onnx-operators_menoh_onnx.pb.cc) [C:\projects\menoh\build\external\onnx\onnx_proto.vcxproj]
C:\protobuf-3.6.0-msvc\include\google/protobuf/stubs/logging.h(100): warning C4251: 'google::protobuf::internal::LogMessage::message_': class 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' needs to have dll-interface to be used by clients of class 'google::protobuf::internal::LogMessage' (compiling source file C:\projects\menoh\build\external\onnx\onnx\onnx-operators_menoh_onnx.pb.cc) [C:\projects\menoh\build\external\onnx\onnx_proto.vcxproj]
...

Although the same commit was built successfully before: https://ci.appveyor.com/project/pfnet-research/menoh/builds/23908116/job/mr3hd0rq0m0vmu83

[msakai]

@durswd, do you have any idea?

[durswd]

I will check it...