add dynamic property mode for qmake

in qmake, the property map is not pre-initialized with the values from
QSettings, as dynamic properties are typically unused, and thus
initializing them would be a waste of time.
consequently, make propertyValue() just a delegate to a QMakeProperty.

Change-Id: I11af5124f810f798214c43704fe49ace03a8f5b8
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>

src/shared/proparser/qmakeglobals.cpp

@@ -282,6 +282,7 @@ QString QMakeGlobals::expandEnvVars(const QString &str) const
     return string;
 }
 
+#ifndef QT_BUILD_QMAKE
 #ifdef PROEVALUATOR_INIT_PROPS
 bool QMakeGlobals::initProperties()
 {
@@ -339,5 +340,6 @@ void QMakeGlobals::setProperties(const QHash<QString, QString> &props)
         properties.insert(ProKey(it.key()), ProString(it.value()));
 }
 #endif
+#endif // QT_BUILD_QMAKE
 
 QT_END_NAMESPACE