[clang] fix: C++ empty record with align lead to va_list out of sync (PR #72197)

[via cfe-commits]

hstk30-hw wrote:

OK, just delete the 

`return ABIArgInfo::getDirect(llvm::Type::getInt8Ty(getVMContext()));` 

from the empty struct codepath, let it fall through to the main path.
Check it again, plz.



https://github.com/llvm/llvm-project/pull/72197