Add sysprop stub for product

This stub is for sysprop_library modules installed to product partition
(which will only contain public properties of platform's or vendor's)

Bug: 171170584
Test: soong test
Change-Id: I8386461833b70847009e12844e1cd91a82ed2981
diff --git a/Android.bp b/Android.bp
index 4c8f6b5..649276e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -86,3 +86,9 @@
     defaults: ["sysprop-library-stub-defaults"],
     soc_specific: true,
 }
+
+java_library {
+    name: "sysprop-library-stub-product",
+    defaults: ["sysprop-library-stub-defaults"],
+    product_specific: true,
+}