Make preferred version work in all cases

Reviewed-by: dt

src/plugins/qt4projectmanager/qtversionmanager.cpp

@@ -242,8 +242,15 @@ void QtVersionManager::updateExamples()
     }
 
     // in SDKs, we want to prefer the Qt version shipping with the SDK
-    QString preferred = Core::ICore::instance()->settings()->value("General/PreferredQMakePath").toString();
+    QSettings *settings = Core::ICore::instance()->settings();
+    QString preferred = settings->value(QLatin1String("PreferredQMakePath")).toString();
+    preferred = QDir::fromNativeSeparators(preferred);
     if (!preferred.isEmpty()) {
+#ifdef Q_OS_WIN
+        preferred = preferred.toLower();
+        if (!preferred.endsWith(QLatin1String(".exe")))
+            preferred.append(QLatin1String(".exe"));
+#endif
         foreach (version, candidates) {
             if (version->qmakeCommand() == preferred) {
                 emit updateExamples(version->examplesPath(), version->demosPath(), version->sourcePath());