run-swarmed.py: Print URLs of task status pages

Convenient to see status of running jobs.

Change-Id: Ia9b04280889aed581f9b08bca6321e57aff30bae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2112110Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752040}

tools/run-swarmed.py

@@ -143,6 +143,10 @@ def _Collect(spawn_result):
   with open(json_file) as f:
     task_json = json.load(f)
   task_ids = [task['task_id'] for task in task_json['tasks']]
+
+  for t in task_ids:
+    print('Task {}: https://chromium-swarm.appspot.com/task?id={}'.format(
+        index, t))
   p = subprocess.Popen(
       [
           'tools/luci-go/swarming',