Avoid `invalid escape sequence` errors on Windows.

Change-Id: I3ed566fb37f235190b5fe91dfd07f575173a6aca
Reviewed-on: https://code-review.googlesource.com/c/re2/+/62711
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
Reviewed-by: Paul Wankadia <junyer@google.com>
1 file changed