Dart does have it's own compiler that targets the native instruction set for supported platforms, e.g. 32-bit and 64-bit ARM for Android and iOS, x86 for Windows and macOS, etc. We're experimenting with bitcode in case Apple decides in the future that they're rather have iOS and/or macOS apps be submitted that way instead of ARM or x86, as they already have for tvOS and watchOS.
Chris Sells PM, Flutter developer experience