Add ART_USE_OPTIMIZING_COMPILER flag.

Change-Id: I86065aec5bfe59729c6a4064a3e54d5b523ca45c
diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index 7b38e5e..7d34dae 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -228,6 +228,10 @@
   art_cflags += -DART_SEA_IR_MODE=1
 endif
 
+ifeq ($(ART_USE_OPTIMIZING_COMPILER),true)
+  art_cflags += -DART_USE_OPTIMIZING_COMPILER=1
+endif
+
 # Cflags for non-debug ART and ART tools.
 art_non_debug_cflags := \
   -O3