Use QFileInfo::exist(f) instead of QFileInfo(f).exists() if possible

Faster.

Change-Id: I91aa67462e11ff3258600d7f158de79942d0dc81
Reviewed-by: Marc Reilly <marc.reilly@gmail.com>
Reviewed-by: Christian Stenger <christian.stenger@digia.com>

src/plugins/qmlprojectmanager/qmlprojectrunconfiguration.cpp

@@ -292,8 +292,7 @@ void QmlProjectRunConfiguration::updateEnabled()
         qmlFileFound = !mainScript().isEmpty();
     }
 
-    bool newValue = QFileInfo(executable()).exists() && qmlFileFound;
-
+    bool newValue = QFileInfo::exists(executable()) && qmlFileFound;
 
     // Always emit change signal to force reevaluation of run/debug buttons
     m_isEnabled = newValue;