Prevent building spatialaudio_quick3d if quick3d is installed and the feature
is disabled.

--- src/CMakeLists.txt.orig	2025-02-20 14:13:07 UTC
+++ src/CMakeLists.txt
@@ -26,7 +26,7 @@ endif()
 if(TARGET Qt::Quick)
     add_subdirectory(multimediaquick)
 endif()
-if(TARGET Qt::Quick3D AND QT_FEATURE_spatialaudio)
+if(TARGET Qt::Quick3D AND QT_FEATURE_spatialaudio AND QT_FEATURE_spatialaudio_quick3d)
     add_subdirectory(spatialaudioquick3d)
 endif()