Enable CC (ART_USE_READ_BARRIER) by default.

Bug: 34084559
Bug: 12687968
Test: boot on angler
Test: test-art-host
Change-Id: I0287b813335b472dd59aa6b94aeeab2da60b9c99
diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index 4c82506..f5a95fa 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -46,6 +46,9 @@
 $(info Disabling ART_BUILD_HOST_DEBUG)
 endif
 
+# Enable the read barrier by default.
+ART_USE_READ_BARRIER ?= true
+
 ART_CPP_EXTENSION := .cc
 
 ifndef LIBART_IMG_HOST_BASE_ADDRESS