Put oat test output on stderr.

Change-Id: Iad318f63263dc5d264d8a84eacedf5065a4e5248
diff --git a/build/Android.common_test.mk b/build/Android.common_test.mk
index 4987567..620444a 100644
--- a/build/Android.common_test.mk
+++ b/build/Android.common_test.mk
@@ -66,7 +66,7 @@
     (mkdir -p $(ART_HOST_TEST_DIR)/failed/ && touch $(ART_HOST_TEST_DIR)/failed/$(1) && \
       echo $(ART_TEST_KNOWN_FAILING) | grep -q $(1) \
         && (echo -e "$(1) \e[91mKNOWN FAILURE\e[0m") \
-        || (echo -e "$(1) \e[91mFAILED\e[0m")))
+        || (echo -e "$(1) \e[91mFAILED\e[0m" >&2 )))
 endef
 
 # Define the command run on test success. $(1) is the name of the test. Executed by the shell.