[clang] [CIR] Handle an empty C++ class in x86_64 callconv lowering (PR #214742)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

IMO, this patch needs to be more generalized I think.  Storing 'is empty' seems like the wrong approach to me.  We should be able to calculate it from the record layout itself based on the contents of it.

https://github.com/llvm/llvm-project/pull/214742