CMake: Use pragma once

Change-Id: I946c819196c5f0f00a13d2f98bae3dff66a43428
Reviewed-by: Alexander Drozdov <adrozdoff@gmail.com>
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/cmakeprojectmanager/builddirmanager.h

@@ -23,8 +23,7 @@
 **
 ****************************************************************************/
 
-#ifndef CMAKE_BUILDDIRMANAGER_H
-#define CMAKE_BUILDDIRMANAGER_H
+#pragma once
 
 #include "cmakecbpparser.h"
 #include "cmakeconfigitem.h"
@@ -129,5 +128,3 @@ private:
 
 } // namespace Internal
 } // namespace CMakeProjectManager
-
-#endif // CMAKE_BUILDDIRMANAGER_H