[clang] [AMDGPU] Synthetic return coerce for aggregates with empty-for-layout members. (PR #197004)

[Marcos Maronas via cfe-commits]

https://github.com/maarquitos14 approved this pull request.

I think this is fine for SPIRV as long as the roundtrip (LLVM->SPIRV->LLVM) keeps the synthetic coerce struct, because then that would be passed to AMDGCN to take care of it as expected.

https://github.com/llvm/llvm-project/pull/197004