message: [vcpkg] Improve error when accessing missing feature
diff: @@ -106,9 +106,14 @@ namespace vcpkg::Dependencies
  return;
  }
  auto maybe_vars = var_provider.get_dep_info_vars(m_spec);
  - const std::vector<Dependency>* qualified_deps =
  - &get_scfl_or_exit().source_control_file->find_dependencies_for_feature(feature).value_or_exit(
  - VCPKG_LINE_INFO);
  + Optional<const std::vector<Dependency>&> maybe_qualified_deps =
  + get_scfl_or_exit().source_control_file->find_dependencies_for_feature(feature);
  + if (!maybe_qualified_deps.has_value())
  + {
  + Checks::exit_with_message(
  + VCPKG_LINE_INFO, "Error: could not find feature '%s' in port '%s'", feature, m_spec.name());
  + }
  + const std::vector<Dependency>* qualified_deps = &maybe_qualified_deps.value_or_exit(VCPKG_LINE_INFO);
  std::vector<FeatureSpec> dep_list;
  if (auto vars = maybe_vars.get())
  