tests/run-multitests.py: Allow to work without sys.stdout on target.

Signed-off-by: Damien George <damien@micropython.org>

tests/run-multitests.py

@@ -32,8 +32,10 @@ import sys
 class multitest:
     @staticmethod
     def flush():
-        if hasattr(sys.stdout, "flush"):
+        try:
             sys.stdout.flush()
+        except AttributeError:
+            pass
     @staticmethod
     def skip():
         print("SKIP")