QtSupport: Move qmake existence check out of *QtVersionFactory::create

Test globally in advance instead. For two factories that means a stricter
check on the qmake executable but with qmake being a host tool the additional
exists/executable check should be in order.

Change-Id: Ib07ef19aeee2d0a19d4c38e178f3e20d22867c2c
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/ios/iosqtversionfactory.cpp

@@ -29,8 +29,6 @@
 #include <qtsupport/qtsupportconstants.h>
 #include <proparser/profileevaluator.h>
 
-#include <QFileInfo>
-
 namespace Ios {
 namespace Internal {