Summary:
`libstdc++` includes `bits/unique_ptr.h` via `include "unique_ptr.h"` in `bits/locale_conv.h` which infer can't redirect to model headers. This leads to compilation issues.
To work around that, redirect include of `locale_conv.h` to include `unique_ptr` via `include <...>` before normal `locale_conv.h`.
Reviewed By: mbouaziz
Differential Revision: D4962314
fbshipit-source-id: d4b9830