[lld] [LLD][COFF] Clarify EC vs. native symbols in diagnostics on ARM64X (PR #130857)

[Jacek Caban via llvm-commits]

cjacek wrote:

> You mentioned that MS link.exe prints the EC disambiguation even for plain arm64ec links, but I presume it only prints the "arm64 native symbol" when linking a hybrid image?

When using -machine:arm64, no suffix is printed.

I rechecked `-machine:arm64ec`, and surprisingly, I could get it to print the native suffix too by passing a native object file. That’s not compatible with how we handle it in lld-link, where we only allow EC object files in this mode, not native ones.

MSVC seems to allow native objects and maintains a separate namespace, similar to ARM64X. I'm not sure why it behaves that way, but if needed, replicating this behavior in lld-link shouldn’t be too difficult.

https://github.com/llvm/llvm-project/pull/130857