cmake-gui: Fix compilation as C++14 with Qt 5.14

Fix code added by commit d7679f6427 (QCMakeCacheView: use non-deprecated
List and Set constructions, 2020-06-10, v3.18.0-rc2~13^2), used
conditionally on Qt 5.14 or above, to compile as C++14.

Source/QtDialog/QCMakeCacheView.cxx

@@ -220,14 +220,14 @@ void QCMakeCacheModel::setProperties(const QCMakePropertyList& props)
 #if QT_VERSION < QT_VERSION_CHECK(5, 14, 0)
     newProps = props.toSet();
 #else
-    newProps = QSet(props.begin(), props.end());
+    newProps = QSet<QCMakeProperty>(props.begin(), props.end());
 #endif
     newProps2 = newProps;
 #if QT_VERSION < QT_VERSION_CHECK(5, 14, 0)
     QSet<QCMakeProperty> oldProps = this->properties().toSet();
 #else
-    QSet<QCMakeProperty> oldProps =
-      QSet(this->properties().begin(), this->properties().end());
+    QSet<QCMakeProperty> oldProps = QSet<QCMakeProperty>(
+      this->properties().begin(), this->properties().end());
 #endif
     oldProps.intersect(newProps);
     newProps.subtract(oldProps);
@@ -236,7 +236,7 @@ void QCMakeCacheModel::setProperties(const QCMakePropertyList& props)
 #if QT_VERSION < QT_VERSION_CHECK(5, 14, 0)
     newProps2 = props.toSet();
 #else
-    newProps2 = QSet(props.begin(), props.end());
+    newProps2 = QSet<QCMakeProperty>(props.begin(), props.end());
 #endif
   }