Fix the build with -DENABLE_TOUCH_EVENTS=OFF

The ebuilds enable touch events unconditionally, but users can
override it with MYCMAKEARGS.

Upstream-bug: https://bugs.webkit.org/show_bug.cgi?id=329222

--- a/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp	2026-10-22 08:54:12.862838700 -0400
+++ b/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp	2026-10-27 21:28:31.916572684 -0400
@@ -2391,10 +2391,12 @@
     g_signal_connect_object(controller, "key-released", G_CALLBACK(webkitWebViewBaseKeyReleased), viewWidget, G_CONNECT_SWAPPED);
     gtk_widget_add_controller(viewWidget, controller);
 
+#if ENABLE(TOUCH_EVENTS)
     controller = gtk_event_controller_legacy_new();
     gtk_event_controller_set_propagation_phase(GTK_EVENT_CONTROLLER(controller), GTK_PHASE_TARGET);
     g_signal_connect_object(controller, "event", G_CALLBACK(webkitWebViewBaseTouchEvent), viewWidget, G_CONNECT_SWAPPED);
     gtk_widget_add_controller(viewWidget, GTK_EVENT_CONTROLLER(controller));
+#endif
 
     auto* gesture = gtk_gesture_click_new();
     gtk_gesture_single_set_button(GTK_GESTURE_SINGLE(gesture), 0);