qbs files: build with Qt5

Help plugin and QmlDesigner have been disabled for Qt5.

Change-Id: I9345d0fd00f9a575333dc972cc7adbdf146cd6cb
Reviewed-by: Alessandro Portale <alessandro.portale@nokia.com>

src/plugins/help/help.qbs

@@ -5,6 +5,8 @@ import "../QtcPlugin.qbs" as QtcPlugin
 QtcPlugin {
     name: "Help"
 
+    condition: qtcore.versionMajor === 4
+    Depends { id: qtcore; name: "qt.core" }
     Depends { name: "qt"; submodules: ['widgets', 'help', 'webkit'] }
     Depends { name: "Core" }
     Depends { name: "Find" }