Make rand_core available to product and vendor

Bug: 270690570

Test: mma in external/rust/crates
Change-Id: I9e2874bd4c0d8a925ce1be9b01bae6a12d5c58de
diff --git a/Android.bp b/Android.bp
index 45a5f93..841b4e1 100644
--- a/Android.bp
+++ b/Android.bp
@@ -58,6 +58,7 @@
         "//apex_available:platform",
         "com.android.virt",
     ],
+    product_available: true,
     vendor_available: true,
 }