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

[Mital Ashok via cfe-commits]

MitalAshok wrote:

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

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