[build] Guard a warning suppression not known to MSVC

This fixes: https://crbug.com/330118187#comment11

Bug: 330118187
Change-Id: Ief074788df6305afc85fb17d165f4beac4b99547
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5432216


Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283842}