roll: third_party/pigweed pw_rpc: Depend on mutex only if enabling PW_RPC_USE_GLOBAL_MUTEX

Since we are not using pw_sync:mutex when disabling global
synchronization, i.e., set PW_RPC_USE_GLOBAL_MUTEX, we should not ask
for a mutex backend.

The change introduces a constraint setting which is used to define the
PW_RPC_USE_GLOBAL_MUTEX, and set up proper build dependency.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/286452
Tests-Not-Needed: Howie Peng <howiepeng@google.com>
Original-Revision: b25f844d44052006b5d2f347e15954a597be0aa4

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: f36b192d1ad8c6..b25f844d440520
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8716367578765990273
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ibd771d5a5cb27bcf2d97f4354874c0a9f3c6eeae
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/286650
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 f36b192..b25f844 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f36b192d1ad8c60f8985b2847e389b1627fc1329
+Subproject commit b25f844d44052006b5d2f347e15954a597be0aa4