Macro runtime_out 

macro_rules! runtime_out {
    ($($arg:tt)*) => { ... };
}

Write a formatted line to standard output, falling back to logs/bootstrap.log.

Takes format! arguments and appends the newline, and evaluates to (), so it is a drop-in for println! anywhere one appears — statement or match arm. A caller that wants to know what became of the line calls to_stdout directly.