Make RRO packages for system_ext

Until now, packages from system_ext don't create RRO packages, instead
it uses static overlay, but to make system_ext common, it should use
RRO.

Bug: 150820813
Test: m && check if there are RRO packages that use from system_ext apps
Change-Id: Id0ddb66adca07a6bb4dda66fbee49fd476ac5342
diff --git a/core/soong_config.mk b/core/soong_config.mk
index abe1923..631846a 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -81,6 +81,7 @@
 $(call add_json_list, DeviceResourceOverlays,            $(DEVICE_PACKAGE_OVERLAYS))
 $(call add_json_list, ProductResourceOverlays,           $(PRODUCT_PACKAGE_OVERLAYS))
 $(call add_json_list, EnforceRROTargets,                 $(PRODUCT_ENFORCE_RRO_TARGETS))
+$(call add_json_list, EnforceRROExemptedTargets,         $(PRODUCT_ENFORCE_RRO_EXEMPTED_TARGETS))
 $(call add_json_list, EnforceRROExcludedOverlays,        $(PRODUCT_ENFORCE_RRO_EXCLUDED_OVERLAYS))
 
 $(call add_json_str,  AAPTCharacteristics,               $(TARGET_AAPT_CHARACTERISTICS))