[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Left some review comments.  Please land https://github.com/llvm/llvm-project/pull/94083 first.

I agree it makes sense to land this in essentially its current form; it seems to be the right algorithm.

https://github.com/llvm/llvm-project/pull/93362