Compile androidnotifier only if widgets are available

The example links against widgets => add proper build-time
guard.

Task-number: QTBUG-136101
Pick-to: 6.9 6.8
Change-Id: I9e279791de5adf4e8bc86a09cb11e96022f9e1ce
Reviewed-by: Assam Boudjelthia <[email protected]>

Author: Juha Vuolle

examples/corelib/platform/CMakeLists.txt

@@ -1,6 +1,6 @@
 # Copyright (C) 2023 The Qt Company Ltd.
 # SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-if(ANDROID)
+if(ANDROID AND QT_FEATURE_widgets)
     qt_internal_add_example(androidnotifier)
 endif()