Fix broken build introduced by ag/3016038

ag/3016038 introduced some build errors on CrOS side. This patch fixes it.

Bug: 66016687
Test: Unittests

Change-Id: I92e9d8843494e1dfc50b4458bb25a61d74d50766
diff --git a/client_library/client_dbus.cc b/client_library/client_dbus.cc
index 426412c..1072836 100644
--- a/client_library/client_dbus.cc
+++ b/client_library/client_dbus.cc
@@ -49,7 +49,9 @@
   return proxy_->AttemptUpdateWithFlags(
       in_app_version,
       in_omaha_url,
-      (at_user_request) ? 0 : kAttemptUpdateFlagNonInteractive,
+      (at_user_request)
+          ? 0
+          : update_engine::UpdateAttemptFlags::kFlagNonInteractive,
       nullptr);
 }