[clang] [clang][X86] Ignore ABI-empty fields and base classes in X86_64 SysV ABI classification algorithm (PR #187814)

[Imple Lee via cfe-commits]

ImpleLee wrote:

FYI, the empty base / empty data member / `[no_unique_address]` is mentioned in the [Itanium C++ ABI](https://itanium-cxx-abi.github.io/cxx-abi/abi.html), but yeah, they are not related to psABI. Maybe you can check it out if you didn't know.

https://github.com/llvm/llvm-project/pull/187814