[roll third_party/pigweed] pw_sync: add lock safety annotations for C++ clang usage

Adds clang thread safety annotations to the interrupt spin lock for
C++ usage. Note that this is only checked when compiling with clang.

C APIs explicitly escape the thread safety annotations.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/40241

third_party/pigweed Rolled-Commits: 597ac2a7e9ec542..cc9ef8367394c28
Roller-URL: https://ci.chromium.org/b/8850139334053799312
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8850139334053799312
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ifb4d2abe2e2c4be09076823c02f15a35311b9fa7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/40641
Reviewed-by: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 597ac2a..cc9ef83 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 597ac2a7e9ec542a61c48f6e3c58c06132ed6a0c
+Subproject commit cc9ef8367394c28f9a57fe0588d6fd9c3f8d0f87