[lld] [LLD][COFF] Add support for the -defArm64Native argument (PR #123850)

[Martin Storsjö via llvm-commits]

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

LGTM, changes like these do work out very neatly thanks to how the class hierarchy is done.

https://github.com/llvm/llvm-project/pull/123850