connection: warn if return from nm_connection_normalize() is unused

If we try to normalize a connection, we generally rely on it being
already valid and be normalized afterwards.

There's one particular case (nmcli interactive add/edit), where we call
it repeatedly on a best-effort basis and don't care about the failures.
Disable the warning there.

src/libnm-core-public/nm-connection.h

@@ -152,10 +152,16 @@ gboolean nm_connection_diff(NMConnection         *a,
 gboolean nm_connection_verify(NMConnection *connection, GError **error);
 NM_AVAILABLE_IN_1_2
 gboolean nm_connection_verify_secrets(NMConnection *connection, GError **error);
-gboolean nm_connection_normalize(NMConnection *connection,
-                                 GHashTable   *parameters,
-                                 gboolean     *modified,
-                                 GError      **error);
+#ifndef __GI_SCANNER__
+#ifdef NETWORKMANAGER_COMPILATION
+_nm_warn_unused_result
+#endif
+#endif
+    gboolean
+    nm_connection_normalize(NMConnection *connection,
+                            GHashTable   *parameters,
+                            gboolean     *modified,
+                            GError      **error);
 
 const char *nm_connection_need_secrets(NMConnection *connection, GPtrArray **hints);
 

src/nmcli/connections.c

@@ -6013,7 +6013,9 @@ read_properties:
      * Keep asking until there's no more things to ask for. */
     do {
         /* This ensures all settings that make sense are present. */
+        NM_PRAGMA_WARNING_DISABLE("-Wunused-result")
         nm_connection_normalize(connection, NULL, NULL, NULL);
+        NM_PRAGMA_WARNING_REENABLE
     } while (nmc->ask && questionnaire_one_optional(nmc, connection));
 
     /* Mandatory settings. No good reason to check this other than guarding the user