stove

The build failure isn't actually due to any layout or implementation details changing in `std::shared_ptr`. The [friend template injection magic](https://github.com/facebook/folly/blob/2197a868fffe71c38a7ec3700344a64318aa230b/folly/concurrency/detail/AtomicSharedPtr-detail.h#L44) assumes a lock policy of `atomic`, which isn't the [default...