pub fn build_session(
    sopts: Options,
    io: CompilerIO,
    bundle: Option<Lrc<FluentBundle>>,
    registry: Registry,
    driver_lint_caps: FxHashMap<LintId, Level>,
    file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
    target_override: Option<Target>
) -> Session