[clang] [ConstantInitBuilder] Use ptradd for self references (PR #222272)

[Nikita Popov via cfe-commits]

nikic wrote:

Okay, it looks like this is less simple than I thought, because relative vtable emission references the vtable address point, which may be in the future (not emitted yet). There's way to solve this, but possible the change is not worthwhile in that case. Closing this for now.

https://github.com/llvm/llvm-project/pull/222272