examples: fix configuring with -no-feature-widgets

It also fails for -no-feature-gui, but since the example depends on
QtWidgets, which implies depending on QtGui, we only check for
QtWidgets here.

Pick-to: 6.2 6.4
Change-Id: I777e540e6c2101ce8f08a5f80ba01b37ff858373
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

examples/corelib/CMakeLists.txt

@@ -1,7 +1,6 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
-add_subdirectory(bindableproperties)
 add_subdirectory(ipc)
 add_subdirectory(mimetypes)
 add_subdirectory(serialization)
@@ -10,3 +9,6 @@ add_subdirectory(platform)
 if(QT_FEATURE_thread)
     add_subdirectory(threads)
 endif()
+if(QT_FEATURE_widgets)
+    add_subdirectory(bindableproperties)
+endif()