message: fix: fix crash on missing return statement
  Turns out the CLI11_PARSE() macro returns not in all cases, but only in case of errors, so additional return in the end is needed (and compiler was right!)
diff: @@ -109,13 +109,9 @@ CPP_FOOTER = """
  CLI11_PARSE(app, argc, argv);
  -#pragma clang diagnostic push
  -#pragma clang diagnostic ignored "-Wreturn-type"
  -#pragma gcc diagnostic push
  -#pragma gcc diagnostic ignored "-Wreturn-type"
  + return 0;
  }
  -#pragma gcc diagnostic pop
  -#pragma clang diagnostic pop
  +
  }// namespace Nextclade
  