[roll third_party/pigweed] pw_watch: Enable watching from non-PW_ROOT

- Enable watching from a directory other than PW_ROOT
- This enables support when the PW_ROOT is not a subdir of the
  PW_PROJECT_ROOT.

Original-Bug: 328083083
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/215735
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 2755100342651a6..5542cfa8150d66a
Roller-URL: https://ci.chromium.org/b/8745310859302882065
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ic32a461659926bcaac2443c13b40736ad0e3362a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/215871
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.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 2755100..5542cfa 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 2755100342651a6b0b41f13c71f432de97ca27e6
+Subproject commit 5542cfa8150d66ab9312372017d29a0d38c020d1