message: GetFallback: append clang.extraArgs
  When compile_commands.json is absent, GetFallback is called to get
  default clang command line when there is no .ccls or .ccls is empty.
diff: @@ -215,6 +215,8 @@ std::vector<const char *> GetFallback(const std::string path) {
  std::vector<const char *> argv{"clang"};
  if (sys::path::extension(path) == ".h")
  argv.push_back("-xobjective-c++-header");
  + for (const std::string &arg : g_config->clang.extraArgs)
  + argv.push_back(Intern(arg));
  argv.push_back(Intern(path));
  return argv;
  }
  