Add ART_USE_READ_BARRIER to product variables.

Bug: 33492005
Test: top-level build for angler.
Change-Id: I12aa2e18487c16423223f110b6dfb0d6dff1e7e8
diff --git a/core/product.mk b/core/product.mk
index e2a5339..93d42fd 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -127,6 +127,7 @@
     VENDOR_PRODUCT_RESTRICT_VENDOR_FILES \
     VENDOR_EXCEPTION_MODULES \
     VENDOR_EXCEPTION_PATHS \
+    PRODUCT_ART_USE_READ_BARRIER \