Fix btchat standalone build: find AndroidExtras before linking it

The btchat standalone build fails because AndroidExtras is linked
which is unknown to CMake at that point. This patch adds
the required find_package call.

Change-Id: I378575a5dd4fe42a89712f903d5cbfa6b539acec
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

examples/bluetooth/btchat/CMakeLists.txt

@@ -35,6 +35,7 @@ target_link_libraries(btchat PUBLIC
 )
 
 if(ANDROID)
+    find_package(Qt6 COMPONENTS AndroidExtras)
     target_link_libraries(btchat PUBLIC
         Qt::AndroidExtras
     )