Have caller of dirmgr_builder() provide Arc.

    /// Only available when compiled with the `experimental-api` feature: this

    /// code is unstable.

    #[cfg(all(feature = "experimental-api", feature = "error_detail"))]

    pub fn dirmgr_builder<B>(mut self, builder: B) -> Self

    pub fn dirmgr_builder<B>(mut self, builder: Arc<dyn DirProviderBuilder<R>>) -> Self

    where

        B: DirProviderBuilder<R> + 'static,

    {

        self.dirmgr_builder = Arc::new(builder);

        self.dirmgr_builder = builder;

        self

    }