qt6_tool: Fix building with tests/examples


Pass -DQT_BUILD_TESTS=ON which is apparently required for the tests to
be built.

Change-Id: I7b0c9dd65330ffa01b1542f4277379067480bb90
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
commit3f7865c20ee89ba9f00b62699c7a21e180172936
parent07e83fe951143178260eee045010700da6351416
authorFriedemann Kleint <Friedemann.Kleint@qt.io>
committerFriedemann Kleint <Friedemann.Kleint@qt.io>
commit timeMon, 8 Sep 2025 08:27:43 +0000