[lld] [ELF] Add --compress-nonalloc-section (PR #84855)

[Petr Hosek via llvm-commits]

petrhosek wrote:

I'd prefer `--compress-sections` as a flag name and mention in the help and documentation that it's only applicable to non-allocated sections. That gives us an option to eventually extend the implementation to allocated sections without having to introduce yet another flag (plus `--compress-sections` is easier to spell and remember).

https://github.com/llvm/llvm-project/pull/84855