[lld] [LLD][COFF] Add support for -includeoptional on ARM64X (PR #126300)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo approved this pull request.

LGTM

As you say this option isn't a standard link.exe option, and I don't think there's much direct use of it; the main use is probably via the mingw driver via the `-u` option. So the main question is what behaviour makes most sense for that flag. In the end, yes, I agree that it probably makes most sense to try to pull in the symbol in both namespaces.

https://github.com/llvm/llvm-project/pull/126300