//! `pac_quickjs` is the `pac-quickjs` feature on every target but Android and iOS, where
//! `rquickjs-sys` ships no bindings and the feature builds without an engine. The library's
//! own code tests this cfg, never the feature.
//!
//! `pac_cfnetwork` is `pac-macos-native` on macOS or `pac-ios-native` on iOS: one CFNetwork
//! implementation behind two per-OS features.
//!
//! `pac_native` is set wherever one of the native PAC resolvers is compiled in.