[llvm] [AArch64] Fix generated types for ARM64EC variadic entry thunk targets (PR #80595)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I haven't really been thinking about cherry-picks for this (and I guess #79774).  Maybe makes sense?  Not sure how complicated the followup isel patch is going to be.

(See https://llvm.org/docs/GitHub.html#backporting-fixes-to-the-release-branches for directions on how to cherry-pick.)

https://github.com/llvm/llvm-project/pull/80595