roll: third_party/pigweed: pw_build: Specify -Wshadow-all for Clang

GCC's `-Wshadow` is stricter than Clang's. Use `-Wshadow-all` in
internal Clang builds. Disable it in a few places as needed.

Original-Fixes: b/346999138
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/216033

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: c6e858e6049da1f..16e6c7a906f3d8d
Roller-URL: https://ci.chromium.org/b/8738512943290676241
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1d87aee43b8dadedf49af95a800d00f47990aff1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/232091
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.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 c6e858e..16e6c7a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c6e858e6049da1f5de6a91240277aec1e4770f0e
+Subproject commit 16e6c7a906f3d8d7c7dab99d5ceb4f3e7ae1843d