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

[Jacek Caban via llvm-commits]

cjacek wrote:

Since this is an LLD extension, we can define its behavior on ARM64X. Unlike `-include`, I applied it to both symbol tables. Because it isn't allowed in `.drectve`, there would be no way to apply it to both tables otherwise. The optional nature of the argument should make it harmless in cases where the intent is to apply it to only one table.

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