[lld] [LLD][COFF] Demangle ARM64EC export names. (PR #87068)

[Eli Friedman via llvm-commits]

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

Are you sure MSVC actually demangles the name, as opposed to getting the demangled name from somewhere else?

https://github.com/llvm/llvm-project/pull/87068