roll: third_party/pigweed 4c6d6de..b9c992f (2 commits)

b9c992f:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/370632 roll: toolchain clang only
cfe4afc:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/370672 pw_bluetooth_proxy: Add pw_async2 to hci/Android.bp

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 4c6d6ded0ece20..b9c992f556f377
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8690945285865917649
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id857db7696ec88edce9b1d19785404451455f013
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/370633
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 4c6d6de..b9c992f 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 4c6d6ded0ece20fd31f9b2a77ad4a3c02111766f
+Subproject commit b9c992f556f3778a9d95bfb3d5dd3b0570e1aa2d