inheritCargoArtifactsHook: symlink dependency rlib and rmeta files

[ipetkov]

Motivation

This is a much simpler (i.e. less ambitious, and easier to land) version of #322

Dependency *.rlib and *.rmeta files never change (as they would only change if Cargo.lock changes which would invalidate the entire build anyway) so we can get away with symlinking them to the inherited artifacts instead of having to deeply copy the files.

Fewer copies means faster builds!

Checklist

• added tests to verify new behavior
• added an example template or updated an existing one
• updated docs/API.md (or general documentation) with changes
• updated CHANGELOG.md