[clang] [ARM, AArch64] Fix passing of structures with aligned base classes (PR #135564)

[Harald van Dijk via cfe-commits]

hvdijk wrote:

Not entirely sure who to ask for reviews, adding @rjmccall for the Itanium C++ ABI aspect as it interacts with the AAPCS ABIs, and @efriedma-quic who approved https://reviews.llvm.org/D46013 originally.

https://github.com/llvm/llvm-project/pull/135564