Notify the queue runner when a build is deleted

src/sql/upgrade-35.sql

@@ -0,0 +1,10 @@
+create function notifyBuildDeleted() returns trigger as $$
+  begin
+    execute 'notify builds_deleted';
+    return null;
+  end;
+$$ language plpgsql;
+
+create trigger BuildDeleted after delete on Builds
+  for each row
+  execute procedure notifyBuildDeleted();