swarm-controller: record builder runs with nix's tail and link the status to them

swarm-controller/src/agent_limits.rs

@@ -509,6 +509,7 @@ pub(crate) mod tests {
             reviews: Arc::default(),
             try_outs: crate::review_classifier::TryOuts::default(),
             runs: crate::review_classifier::runs::Runs::Live(None),
+            builds: crate::builder::runs::Builds::Live(None),
             alerts: None,
         }
     }