Build clang builds with -Werror (#69712)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/69712
Test Plan: Imported from OSS
Reviewed By: seemethere
Differential Revision: D32997002
Pulled By: malfet
fbshipit-source-id: 8ebb5a955f8ae2d3fb67bc70636a2b1d66010c84
