Fix Flatbuffer build issue. (#19296)
### Description
Building on g++ 13.2.0 results in -Wstringop-overread errors on Linux.
This commit addresses the flatbuffer build issue with the following
changes:
1. Remove the Werror flag in the flarbuffer patch.
2. Add a compilation option to suppress the 'stringop-overflow' error in
the Flatbuffers within the xnnpack provider.
### Motivation and Context
https://github.com/google/flatbuffers/issues/8119
https://github.com/microsoft/onnxruntime/pull/19239
Signed-off-by: Phoebe Chen <phoebe.chen@sifive.com>
