[clang] [llvm] Reland "[llvm][ADT] Refactor PointerUnion to use PunnedPointer. NFC." (PR #188242)

[Michael Buch via cfe-commits]

Michael137 wrote:

> @Michael137 how can I repro this? I can take a look shortly but I don't know what enables these tests

That'd be appreciated thanks! Happy to help with debugging/fixing this.

Does this repro for you if you add `cross-project-tests` to your `LLVM_ENABLE_PROJECT` and then build the `check-cross-project` target? I *think* you don't need a local LLDB to run these tests

https://github.com/llvm/llvm-project/pull/188242