CMake: Only offer kits with a cmake set up!

Change-Id: Icb4b539e009c9dc5bdf40f8d8b887bb65755b48b
Reviewed-by: Cristian Adam <cristian.adam@gmail.com>
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/cmakeprojectmanager/cmakeproject.h

@@ -118,6 +118,8 @@ public:
 
     bool requiresTargetPanel() const override;
 
+    bool supportsKit(ProjectExplorer::Kit *k, QString *errorMessage = 0) const override;
+
 signals:
     /// emitted after parsing
     void buildTargetsChanged();