fuzz: set a size limit

Otherwise it's possible for the fuzzer to build a regex that is big
enough to timeout on a big haystack.

fuzz/fuzz_targets/fuzz_regex_match.rs

@@ -14,7 +14,9 @@ fuzz_target!(|data: &[u8]| {
  let char_index = data.char_indices().nth(split_off_point);
  if let Some((char_index, _)) = char_index {
  let (pattern, input) = data.split_at(char_index);
- if let Ok(re) = regex::Regex::new(pattern) {
+ let result =
+ regex::RegexBuilder::new(pattern).size_limit(1 << 20).build();
+ if let Ok(re) = result {
  re.is_match(input);
  }
  }