message: Print error message when there is a syntax error in triplet file
  As it is now vcpkg fails silently (actually, it outputs two empty lines).
diff: @@ -489,7 +489,7 @@ namespace vcpkg::Build
  {"CMAKE_TRIPLET_FILE", triplet_file_path},
  });
  const auto ec_data = System::cmd_execute_and_capture_output(cmd_launch_cmake);
  - Checks::check_exit(VCPKG_LINE_INFO, ec_data.exit_code == 0);
  + Checks::check_exit(VCPKG_LINE_INFO, ec_data.exit_code == 0, ec_data.output);
  const std::vector<std::string> lines = Strings::split(ec_data.output, "\n");
  