Fix infinite recursion during IR emission if a constant-initialized...

Fix infinite recursion during IR emission if a constant-initialized lifetime-extended temporary object's initializer refers back to the same object.

`GetAddrOfGlobalTemporary` previously tried to emit the initializer of
a global temporary before updating the global temporary map. Emitting the
initializer could recurse back into `GetAddrOfGlobalTemporary` for the same
temporary, resulting in an infinite recursion.

Reviewed By: rjmccall

Differential Revision: https://reviews.llvm.org/D97733