Feature request: Warn about reverse or cyclic dependencies

[LarsGullik]

For larger projects or projects in general where multiple linker might be used for
various build targets it nice to have some help in avoiding link-order issues.

Mold mostly does away with the issues, but link-order issues can sneak in.
Lld have options --warn-backrefs and --warn-backrefs-exclude that helps
with keeping the link order compatible with the older UNIX style linkers.

Getting support for same or similar functionality in mold would be great.