fix(cmake): exclude demo app from product integration

CMakeLists.txt

@@ -78,6 +78,11 @@ option(
     "Install update-client runtime assets from this project"
     ${UPDATE_CLIENT_IS_STANDALONE}
 )
+option(
+    UPDATE_CLIENT_BUILD_DEMO_APP
+    "Build the standalone MainApp integration demo"
+    ${UPDATE_CLIENT_IS_STANDALONE}
+)
 
 list(PREPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 include(UpdateClientDependencies)
@@ -137,10 +142,20 @@ target_link_libraries(UpdateClientUpdaterLogic
 
 add_subdirectory(Launcher)
 add_subdirectory(Updater)
-add_subdirectory(MainApp)
 
-foreach(_update_client_primary_target IN ITEMS
-        Bootstrap Common UpdateClientUpdaterLogic Launcher Updater MainApp)
+set(_update_client_primary_targets
+    Bootstrap
+    Common
+    UpdateClientUpdaterLogic
+    Launcher
+    Updater
+)
+if(UPDATE_CLIENT_BUILD_DEMO_APP)
+    add_subdirectory(MainApp)
+    list(APPEND _update_client_primary_targets MainApp)
+endif()
+
+foreach(_update_client_primary_target IN LISTS _update_client_primary_targets)
     add_dependencies("${_update_client_primary_target}" UpdateClientNoHanCheck)
 endforeach()