Summary:
We currently bump it for clang+tsan because the clang implementation of tsan historically implements the historical pre-c++17 rule even post-c++17. But to enable libstdc++ assertions, we must also bump it for for some versions of libstdc++ when assertions are enabled.

The assertions are removed in libstdc++ trunk: https://github.com/gcc-mirror/gcc/commit/dba1ab212292839572fda60df00965e094a11252. They remain in libstdc++11.2.

Reviewed By: ot

Differential Revision: D31593055

fbshipit-source-id: a339306e86452c4bb6d9d821cd28038ab6f49767