message: [vcpkg] Record output from build process into log file
diff: @@ -521,11 +521,24 @@ namespace vcpkg::Build
  else
  return System::cmd_execute_modify_env(build_env_cmd, clean_env);
  });
  -
  - const int return_code = System::cmd_execute(command, env);
  #else
  - const int return_code = System::cmd_execute_clean(command);
  + const auto& env = System::get_clean_environment();
  #endif
  + auto stdoutlog =
  + paths.buildtrees / action.spec.name() / ("stdout-" + action.spec.triplet().canonical_name() + ".log");
  + std::ofstream out_file(stdoutlog.native().c_str(), std::ios::out | std::ios::binary | std::ios::trunc);
  + Checks::check_exit(VCPKG_LINE_INFO, out_file, "Failed to open '%s' for writing", stdoutlog.u8string());
  + const int return_code = System::cmd_execute_and_stream_data(
  + command,
  + [&](StringView sv) {
  + System::print2(sv);
  + out_file.write(sv.data(), sv.size());
  + Checks::check_exit(
  + VCPKG_LINE_INFO, out_file, "Error occurred while writing '%s'", stdoutlog.u8string());
  + },
  + env);
  + out_file.close();
  +
  // With the exception of empty packages, builds in "Download Mode" always result in failure.
  if (action.build_options.only_downloads == Build::OnlyDownloads::YES)
  {
  