Add pragma once to utils.hpp

Change-Id: If86f28cb0de585d56a0fae9e4f7ddf0bd6cf718e
diff --git a/src/utils.hpp b/src/utils.hpp
index 2f93bfb..ef24e60 100644
--- a/src/utils.hpp
+++ b/src/utils.hpp
@@ -8,6 +8,8 @@
 /*! \file utils.hpp
     \brief A header containing utility functions
 */
+#pragma once
+
 #include <string>
 #include "ast_path.hpp"
 #include "ast_values.hpp"