Qt-Qwt dependency in superbuild
This is a small MR to warn user that are disabling Qt but not Qwt that the Qt module will still be build as QWT depends on it.
As it just produces a message we can discuss on whether we are creating a depending option for Qwt or we force the value of OTB_USE_QT
to ON
if OTB_USE_QWT=ON
.