[clang] [llvm] [LLVM] Fix incorrect alignment on AMDGPU variadics (PR #96370)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> Patch should not land. Need to know what bug this was trying to address to guess at what the right fix would be.

My understanding was that the variadics did lowering to a struct with a minimum alignment of four. This currently *doesn't* do that, hence my confusion. The current lowering provides no padding, which I now see is a deliberate choice to save on stack presumably. The issue I had was that I laid out my `printf` code with the assumption that the buffer was a struct, so now it won't work when copied to another target via RPC because it's not the correct alignment.

https://github.com/llvm/llvm-project/pull/96370