Compile error due to std::move

[matthill]

Compiling against the latest software on Ubuntu 20.04 and GCC 9, I get the following error:

cmake/external/onnx-tensorrt/builtin_op_importers.cpp: In function ‘std::vectornvinfer1::PluginField onnx2trt::{anonymous}::loadFields(string_map<std::vector >&, const OnnxAttrs&, const nvinfer1::PluginFieldCollection*)’:

cmake/external/onnx-tensorrt/builtin_op_importers.cpp:3737:21: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move]
3737 | return std::move(fields);
| ~~~~~~~~~^~~~~~~~

I see some discussion here: http://www.cplusplus.com/forum/general/186411/

[kevinch-nv]

This was fixed in #568. Closing.