CMake: Make sure there is a "clean" target

Change-Id: I9e3eb49b7f5a2d7d5c89a53969c4703b3ce99330
Reviewed-by: Cristian Adam <cristian.adam@gmail.com>
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>

src/plugins/cmakeprojectmanager/cmakeproject.h

@@ -65,7 +65,8 @@ class CMakeManager;
 enum TargetType {
     ExecutableType = 0,
     StaticLibraryType = 2,
-    DynamicLibraryType = 3
+    DynamicLibraryType = 3,
+    UtilityType = 64
 };
 
 struct CMAKE_EXPORT CMakeBuildTarget