CMake: Fix examples that use 'shared' project when using a static Qt

When using a static Qt, linking of examples that use the 'shared' Qml
module would fail with the following error

Undefined symbols for architecture x86_64:
  "qt_static_plugin_sharedPlugin()", referenced from:
  StaticsharedPluginPluginInstance::StaticsharedPluginPluginInstance()
  in window_shared_init.cpp.o

This happened because the 'shared' project pre-created its
plugin target with qt_add_library instead of qt_add_plugin.

qt_add_plugin passes an additional QT_STATICPLUGIN compile definition
when compiling the moc'ed file to ensure that the QT_MOC_EXPORT_PLUGIN
macro creates a qt_plugin_instance_PLUGIN_NAME symbol.

Unfortunately we can't use qt_add_plugin for shared Qt builds, because
some of the projects link directly against the plugin target and it's
not possible to link against a MODULE_LIBRARY target which
qt_add_plugin creates in shared Qt build.

We could try to conditionally switch between using qt_add_library for
a shared Qt build and qt_add_plugin for a static Qt build, but that
further complicates the build system code because it requires
specifying a class name and plugin type explicitly.

Remove the direct linkage against the libraries in the examples and
instead rely on plugin loading.
This simplifies the logic of not having to pre-create a target.

Amends 7b6eea37ae

Pick-to: 6.2
Fixes: QTBUG-96805
Change-Id: I5b2f3992ccda29b59f1e99748005381c73daca69
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

examples/quick/animation/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(animationexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    animation_shared
 )
+add_dependencies(animationexample animation_shared)
 
 qt_add_qml_module(animationexample
     URI animation

examples/quick/delegatechooser/CMakeLists.txt

@@ -26,8 +26,8 @@ target_link_libraries(delegatechooserexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    delegatechooser_shared
 )
+add_dependencies(delegatechooserexample delegatechooser_shared)
 
 qt_add_qml_module(delegatechooserexample
     URI delegatechooser

examples/quick/shapes/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(shapesexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    shapes_shared
 )
+add_dependencies(shapesexample delegatechooser_shared)
 
 qt_add_qml_module(shapesexample
     URI shapes

examples/quick/shared/CMakeLists.txt

@@ -1,5 +1,3 @@
-qt_add_library(${PROJECT_NAME}_shared)
-
 set_source_files_properties(CheckBox.qml TabSet.qml TextField.qml
     PROPERTIES
         QT_QML_SOURCE_VERSIONS 2.1

examples/quick/text/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(textexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    text_shared
 )
+add_dependencies(textexample text_shared)
 
 qt_add_qml_module(textexample
     URI text

examples/quick/threading/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(threadingexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    threading_shared
 )
+add_dependencies(threadingexample threading_shared)
 
 qt_add_qml_module(threadingexample
     URI threading

examples/quick/touchinteraction/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(touchinteractionexample PUBLIC
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    touchinteraction_shared
 )
+add_dependencies(touchinteractionexample touchinteraction_shared)
 
 qt_add_qml_module(touchinteractionexample
     URI touchinteraction

examples/quick/views/CMakeLists.txt

@@ -34,8 +34,8 @@ target_link_libraries(viewsexample PRIVATE
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    views_shared
 )
+add_dependencies(viewsexample views_shared)
 
 qt_add_qml_module(viewsexample
     URI views

examples/quick/window/CMakeLists.txt

@@ -45,8 +45,8 @@ target_link_libraries(windowexample PRIVATE
     Qt::Gui
     Qt::Qml
     Qt::Quick
-    window_shared
 )
+add_dependencies(windowexample window_shared)
 
 install(TARGETS windowexample
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"