Function pre_eval_system_time 

fn pre_eval_system_time(
    args: &[Arg],
    env: &Environment,
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Measure the wall-clock time to evaluate an expression.

Returns a proc_time object (named numeric vector with class "proc_time"). User and system CPU times are reported as 0 since we only measure wall-clock time.

@param expr the expression to time @return proc_time vector c(user.self=0, sys.self=0, elapsed=)