Fix hello example benchmark for PG.

Consumes output of compilation with is otherwise too large for golem.

Change-Id: I0aec9d4e1434075ed5fd83daabd73422f1c8d423
diff --git a/tools/test_helloexample.py b/tools/test_helloexample.py
index 941b031..abda493 100755
--- a/tools/test_helloexample.py
+++ b/tools/test_helloexample.py
@@ -241,7 +241,7 @@
     for cmd in cmds:
       fullcmd = cmd_prefix + cmd
       utils.PrintCmd(fullcmd)
-      subprocess.check_call(fullcmd)
+      subprocess.check_output(fullcmd)
     dt = time.time() - t0
 
     if args.print_memoryuse: