roll: third_party/pigweed 6667d2c..bcefbab (3 commits)

bcefbab:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/284277 pw_kernel: Remove the timers dependency on the cortex-rt crate
8866349:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/284394 pw_flatbuffers: Use STRING for pw_flatbuffers_FLATC_FLAGS
a79430f:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/284373 third_party/boringssl: Use pw_external_boringssl in gn

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 6667d2c2a67fac..bcefbaba1a32e6
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8717231185969430097
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I8370c941e48e7269a7f2d33192d8da7d3f51a182
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/284681
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 6667d2c..bcefbab 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 6667d2c2a67fac82dbcb53e5a479b96fa30e7526
+Subproject commit bcefbaba1a32e6fbe76ebc9ea1467bc96cf89bbc