[roll third_party/pigweed] pw_bluetooth: Add cmake to usage guide

Test: Manual review of generated doc
Original-Bug: 326499587
Original-Bug: 326499650
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/200012

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 16ca90925a98bdc..b8c700540dbb7c0
Roller-URL: https://ci.chromium.org/b/8752209191229444849
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I881d9992f35e58148b052b3b12a6ea94498c86b3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/200895
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 16ca909..b8c7005 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 16ca90925a98bdcbe294618973adff00e2649853
+Subproject commit b8c700540dbb7c048eb16a088ec899e736532843