Also send bionicbb logs to a file.

Change-Id: If9a6fdbe004e3b4bb7d868b7255f83c232759f80
diff --git a/tools/bionicbb/bionicbb.py b/tools/bionicbb/bionicbb.py
index 20d6460..a786b27 100644
--- a/tools/bionicbb/bionicbb.py
+++ b/tools/bionicbb/bionicbb.py
@@ -120,6 +120,10 @@
 
 if __name__ == "__main__":
     logging.basicConfig(level=logging.INFO)
+    logger = logging.getLogger()
+    fh = logging.FileHandler('bionicbb.log')
+    fh.setLevel(logging.INFO)
+    logger.addHandler(fh)
 
     # Prevent the job from being rescheduled by the reloader.
     if os.environ.get('WERKZEUG_RUN_MAIN') == 'true':