Revert "contrib: qt: don't patch create_libtool value"

This reverts commit cee6cee6.

Unfortunately, removing create_libtool from CONFIG in the toolchain file gets overridden when it is added to CONFIG again in qt_module.prf.

Qt itself adds it to CONFIG for "!lib_bundle:unix", indeed in the Windows contrib archive, libQt5Bootstrap.la can be spotted (as this is for the native build only). Also, when building for Debian, all Qt modules will install .la files, like libQt5Core.la.

As qt_module.prf is the only place in the whole of Qt where this is added to CONFIG, it should be sufficient to patch it here.