onnxruntime

Windows build fix for on device training training. (#13354)

### Description
This is a fix for on device training wheel build.

### Motivation and Context
when building linux wheel it treats PathString same as std::string, but
when trying to build the wheel on windows it fails because we needed to
cast the std::string to a PathString.

This error was found manually because there is no pipeline that uses the
--enable_training_on_device for windows.

Co-authored-by: Adam Louly <adamlouly@microsoft.com@orttrainingdev7.d32nl1ml4oruzj4qz3bqlggovf.px.internal.cloudapp.net>