Fix breakage when RE2_USE_ICU is defined.
Fix breakage when RE2_USE_ICU is defined.

Change-Id: I095e9a07ddbced2fef1f05313277b10b42c9e73a
Reviewed-on: https://code-review.googlesource.com/c/re2/+/59133
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2