QtSupport: Use better value for remote QTDIR env variables

It does not really seem to be used in earnetst anymore, but
it shouldn't contain the scheme://host decoration.

Change-Id: Ieba416e0a73d247d80d1c5cce79858b1896e13ea
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qtsupport/baseqtversion.cpp

@@ -1612,7 +1612,7 @@ QSet<Id> QtVersion::features() const
 void QtVersion::addToEnvironment(const Kit *k, Environment &env) const
 {
     Q_UNUSED(k)
-    env.set("QTDIR", hostDataPath().toUserOutput());
+    env.set("QTDIR", hostDataPath().nativePath());
 }
 
 // Some Qt versions may require environment settings for qmake to work