[llvm-branch-commits] [llvm] Backport ARM64EC variadic args fixes to LLVM 18 (PR #81800)

[Eli Friedman via llvm-branch-commits]

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

Looks fine, but I think merging might need to wait for a point release?  CC @tstellar .

https://github.com/llvm/llvm-project/pull/81800