[clang] [llvm] [Clang] Fix definition of layout-compatible to ignore empty classes (PR #92103)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> @dwblaikie This patch will bring Clang in line with GCC and MSVC: https://godbolt.org/z/nj715zbsW

would the change be ABI incompatible with previous versions of clang? If so, then it'll need to be versioned in Clang's ClangABI handling, so that platforms (like Sony's Playstation, and Apple's platforms) that are only interested in Clang ABI compatibility can retain the old behavior.

@rjmccall might have an interest in whether this is an ABI thing Apple cares about
@pogo59 not sure who over at Sony's the best person to check on sony ABI things

https://github.com/llvm/llvm-project/pull/92103