[roll third_party/pigweed] pw_build: Dependency fixes

- Handle public_deps as well as deps in pw_mirror_tree.
- Have the Python .install target avoid unnecessary reinstalls, but
  have dependents re-run when any files change. This is done by
  splitting the installs into a separate target and having .install
  depend on it and the target that represents the source files.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39202

third_party/pigweed Rolled-Commits: 7a3c6525a6f231b..446f24c4074ba73
Roller-URL: https://ci.chromium.org/b/8851748905057676672
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8851748905057676672
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0fa80cb1355f67fd11c10d1dd8ab05c87d82dd3f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/39266
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 7a3c652..446f24c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7a3c6525a6f231b1984816cd1b37af58b2552424
+Subproject commit 446f24c4074ba733b3cc9505a3dd59b51e67d417