Don't use typeid without RTTI in UniqueInstance
Don't use typeid without RTTI in UniqueInstance

Summary: The class depends on RTTI. It's a sanity check that crashes if two instances of a singleton are created. So doing nothing in `-fno-rtti` code is fine.

Reviewed By: yfeldblum

Differential Revision: D29630207

fbshipit-source-id: 4976f72394086afe12e224e40fe955636108e713

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly