[libcxx-commits] [libcxx] [libc++] Fix `regex_search` to match `$` alone with `match_default` flag (PR #78845)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

LGTM -- I checked and this should fix all reported regressions around this.

https://github.com/llvm/llvm-project/pull/78845