Exclude qtdiag when QtGui is not available.

Task-number: QTBUG-39118
Change-Id: I54f6879ef58e5b7b7bc2c20840524f4af5433921
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

src/src.pro

@@ -29,11 +29,10 @@ qtHaveModule(dbus): SUBDIRS += qdbus
 
 win32|winrt:SUBDIRS += windeployqt
 winrt:SUBDIRS += winrtrunner qtd3dservice
+qtHaveModule(gui):!android:!ios:!qnx:!wince*:!winrt*:SUBDIRS += qtdiag
 
 qtNomakeTools( \
     pixeltool \
     qtconfig \
     macdeployqt \
 )
-
-!android:!ios:!qnx:!wince*:!winrt*:SUBDIRS += qtdiag