Add ART_USE_READ_BARRIER to product variables.

Bug: 33492005
Test: top-level build for angler.
Change-Id: I12aa2e18487c16423223f110b6dfb0d6dff1e7e8
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 94cd4a0..f488566 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -62,7 +62,9 @@
 	echo '    "CrossHost": "$(HOST_CROSS_OS)",'; \
 	echo '    "CrossHostArch": "$(HOST_CROSS_ARCH)",'; \
 	echo '    "CrossHostSecondaryArch": "$(HOST_CROSS_2ND_ARCH)",'; \
-	echo '    "Safestack": $(if $(filter true,$(USE_SAFESTACK)),true,false)'; \
+	echo '    "Safestack": $(if $(filter true,$(USE_SAFESTACK)),true,false),'; \
+	echo ''; \
+	echo '    "ArtUseReadBarrier": $(if $(filter true,$(PRODUCT_ART_USE_READ_BARRIER)),true,false)'; \
 	echo '}') > $(SOONG_VARIABLES_TMP); \
 	if ! cmp -s $(SOONG_VARIABLES_TMP) $(SOONG_VARIABLES); then \
 	  mv $(SOONG_VARIABLES_TMP) $(SOONG_VARIABLES); \