PyTorch is already built with _GLIBCXX_USE_CXX11_ABI=0. So you have to also set this flag when compiling the C++ extension. In PyTorch 1.0 this should already be done for you, see https://github.com/pytorch/pytorch/blob/master/torch/utils/cpp_extension.py#L390 239.
The best way to solve this problem in any case is to compile Pytorch from source and use that same compiler for the extension. Then all problems go away.