Function activate_injected_dep

fn activate_injected_dep(
    injected: Option<CrateNum>,
    list: &mut DependencyList,
    replaces_injected: &dyn Fn(CrateNum) -> bool,
)

Given a list of how to link upstream dependencies so far, ensure that an injected dependency is activated. This will not do anything if one was transitively included already (e.g., via a dylib or explicitly so).

If an injected dependency was not found then we’re guaranteed the metadata::creader module has injected that dependency (not listed as a required dependency) in one of the session’s field. If this field is not set then this compilation doesn’t actually need the dependency and we can also skip this step entirely.