build native tests for 32-bit and 64-bit

32-bit tests will build into /data/nativetest
64-bit tests will build into /data/nativetest64

Change-Id: I31492c7d1273ba18bb2577fae150008a214c3bf4
diff --git a/core/native_test.mk b/core/native_test.mk
index fc08f79..bc7f2e7 100644
--- a/core/native_test.mk
+++ b/core/native_test.mk
@@ -5,4 +5,6 @@
 
 include $(BUILD_SYSTEM)/target_test_internal.mk
 
+LOCAL_MULTILIB := both
+
 include $(BUILD_EXECUTABLE)