[llvm] [AArch64] Skip over shadow space for ARM64EC entry thunk variadic calls (PR #80994)

[Daniel Paoliello via llvm-commits]

dpaoliello wrote:

> It looks like the regression tests are failing on the buildbots?

`arm64ec-entry-thunks.ll` failed, I guess the baseline needs to be updated?

https://github.com/llvm/llvm-project/pull/80994