* With `--max-jobs 0', print a nicer error message than "Assertion

`!awake.empty()' failed."

src/libstore/build.cc

@@ -2550,9 +2550,13 @@ void Worker::run(const Goals & _topGoals)
         /* Wait for input. */
         if (!children.empty() || !waitingForAWhile.empty())
             waitForInput();
-        else
+        else {
+            if (maxBuildJobs == 0) throw Error(
+                "unable to start any build; either increase `--max-jobs' "
+                "or enable distributed builds");
             assert(!awake.empty());
         }
+    }
 
     /* If --keep-going is not set, it's possible that the main goal
        exited while some of its subgoals were still active.  But if