message: Don't print regressions header when there are no regressions.
diff: @@ -488,8 +488,7 @@ namespace vcpkg::Commands::CI
  const std::string& ci_baseline_file_name,
  bool allow_unexpected_passing)
  {
  - LocalizedString output = msg::format(msgCiBaselineRegressionHeader);
  - output.appendnl();
  + LocalizedString output;
  for (auto&& port_result : result.summary.results)
  {
  switch (port_result.build_result.code)
  @@ -521,7 +520,16 @@ namespace vcpkg::Commands::CI
  }
  }
  - fputs(output.data().c_str(), stderr);
  + auto output_data = output.extract_data();
  + if (output_data.empty())
  + {
  + return;
  + }
  +
  + LocalizedString header = msg::format(msgCiBaselineRegressionHeader);
  + header.appendnl();
  + output_data.insert(0, header.extract_data());
  + fwrite(output_data.data(), 1, output_data.size(), stderr);
  }
  void perform_and_exit(const VcpkgCmdArguments& args,
  