The 'z' length modifier for {size_t} in format strings was introduced
with C99, hence it is available in all environments we support.

R=jgruber@chromium.org, mlippautz@chromium.org

Bug: v8:9183
Change-Id: I1bc2abec3f9c7b38186128202fef4719853de7d4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1613243Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61536}