[build] Add system_image property to package()

Change-Id: Iac0477a758b6a6e0fbfc7df9fd673c8424aa3927
diff --git a/BUILD.gn b/BUILD.gn
index 944b9e8..f2e2b5f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -75,6 +75,7 @@
 
 package("package") {
   package_name = "sqlite"
+  system_image = true
 
   deps = [
     ":shell",