make use of qtHaveModule()

Change-Id: I440b609d23570293f21f21a2cb31854366d06bf7
Reviewed-by: Tasuku Suzuki <stasuku@gmail.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>