[roll third_party/pigweed] pw_build: Only use -Wextra-semi on C++ files with GCC

GCC doesn't like it when -Wextra-semi is a C flag, and only allows it
when compiling C++.

Original-Bug: b/306734552, b/301262374
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/177171

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 26ccfc66c181be7..35460f87885e0a5
Roller-URL: https://ci.chromium.org/b/8766663225457884817
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2a2c4d5851fab8ed26540c017462da6fb1506ba3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/177181
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 26ccfc6..35460f8 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 26ccfc66c181be7da3580cc44bf017732b73c4ab
+Subproject commit 35460f87885e0a56724a79c9523e600766e417f5