[lld] [LLD][COFF] Support CF guards on ARM64X (PR #128440)

[Jacek Caban via llvm-commits]

cjacek wrote:

Sorry about that. We're missing `classof` for `ECExportThunkChunk`, so the `dyn_cast_or_null` is not right. It should be easy to fix, I'm working on it.

https://github.com/llvm/llvm-project/pull/128440