Switch to -O2. -O0 benefits no-one.

Change-Id: I0ce5406000701b11455ffcc4be90e78bccb5d92d
diff --git a/build/Android.common.mk b/build/Android.common.mk
index 575c810..de2622a 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -25,7 +25,7 @@
 	dalvik/libdex
 
 ART_CFLAGS := \
-	-O0 \
+	-O2 \
 	-ggdb3 \
 	-Wall \
 	-Werror \