ART: Blacklist test 912 for target

As usual, black-list an agent test for the target.

Bug: 31684578
Test: m test-art-host-run-test-912-classes
Change-Id: I9afd9f88bf794e6d90d1ea5cd259de4fbed7e27e
diff --git a/test/Android.run-test.mk b/test/Android.run-test.mk
index cfb05f9..2251b7e 100644
--- a/test/Android.run-test.mk
+++ b/test/Android.run-test.mk
@@ -278,6 +278,7 @@
   909-attach-agent \
   910-methods \
   911-get-stack-trace \
+  912-classes \
 
 ifneq (,$(filter target,$(TARGET_TYPES)))
   ART_TEST_KNOWN_BROKEN += $(call all-run-test-names,target,$(RUN_TYPES),$(PREBUILD_TYPES), \