message: Explain why iterators aren't used in `build_map`
diff: @@ -5,6 +5,8 @@ use std::collections::HashMap;
  pub(crate) fn build_map<'key, 'value, const N: usize>(
  array: [(&'key str, Option<&'value str>); N],
  ) -> HashMap<&'key str, &'value str> {
  + // Use a manual for loop instead of iterators so we can call `with_capacity` and avoid
  + // reallocating.
  let mut map = HashMap::with_capacity(N);
  for (key, value) in array {
  if let Some(value) = value {
  