Function gather_active_jobs 

pub(crate) fn gather_active_jobs<'tcx>(
    tcx: TyCtxt<'tcx>,
    qmap: &mut QueryMap<'tcx>,
    require_complete: bool,
) -> Option<()>

Internal per-query plumbing for collecting the set of active jobs for this query.

Should only be called through PER_QUERY_GATHER_ACTIVE_JOBS_FNS.