Adapt CustomTarget_postprocess/check_dynamic_objects

Adapt CustomTarget_postprocess/check_dynamic_objects

...to 441d8ed9be0e7f831b455a69b8688dcb79a8bc00 "tdf#145735 avmedia qt: Use
QtMultimedia for Qt 6 media playback", which caused

> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6Core.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6Gui.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6Widgets.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6Network.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6Multimedia.so.6
> instdir/program/libvclplug_qt6lo.so has suspicious NEEDED: libQt6Multimedia.so.6
> instdir/program/libvclplug_qt6lo.so has suspicious NEEDED: libQt6MultimediaWidgets.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libQt6MultimediaWidgets.so.6
> instdir/program/libavmediaqt6.so has suspicious NEEDED: libxcb.so.1

Change-Id: Iccbef5048ddb8375da33517ca0f797fe8f8d5565
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/168093
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
Tested-by: Jenkins