Build an -Wextra around c10 (#59853)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/59853
Test Plan: Sandcastle
Reviewed By: ngimel
Differential Revision: D29016682
fbshipit-source-id: f6c5f32464d57dbd60b59b5f9e2234ef2c39f1c1
