Macro futures_lite

macro_rules! futures_lite {
    () => { ... };
    (if { $($p:tt)* } else { $($n:tt)* }) => { ... };
    ($($p:tt)*) => { ... };
}

Indicates futures-lite will be used for the implementation of block_on.

This macro passes the provided code because #[cfg(feature = "futures-lite")] is currently active.