[roll third_party/pigweed] pw_string: Fix the warning of format string

bypass the format string warning for va_lists in the pw_string/format.cc
and pw_string/string_builder.cc on darwin build.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/95600

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 714c790bde63cb2..9816c35905e632d
Roller-URL: https://ci.chromium.org/b/8813352709106647137
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8813352709106647137
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iaa9ab36858d0aebd80c3611ec0d7a69320253303
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/95644
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
1 file changed