fix build on old clang compilers

Author: thelfer

mfront/include/MFront/CodeGeneratorUtilities.hxx

@@ -378,7 +378,7 @@ namespace mfront {
    * \param[in] ln: line number
    * \param[in] f: file name
    */
-  MFRONT_VISIBILITY_EXPORT [[nodiscard]] std::string printLinePragma(
+  MFRONT_VISIBILITY_EXPORT std::string printLinePragma(
       const std::size_t, std::string_view);
 
 }  // end of namespace mfront