[roll third_party/pigweed] build: GN static_analysis polish

Some python fixes and documentation updates.
- Refine the implementation of the source filter
  to match relative paths only.

Original-Bug: 45
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/59286

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9f056bc1fea45ca..dd46587b659063d
Roller-URL: https://ci.chromium.org/b/8835461573409766049
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8835461573409766049
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7260bdea6ec695280540246fccbba4aaabb1f611
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/61661
Bot-Commit: 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 9f056bc..dd46587 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9f056bc1fea45ca38b535ee47dfc893d48e3eea1
+Subproject commit dd46587b659063d9430f6d1533545e885c0a5ac2