[roll third_party/pigweed] pw_build: Fine tune python_runner's PYTHONPATH logic

If no __init__.py exists for a given python_dep, don't add it to the
PYTHONPATH.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97790

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 4331b174c459809..3f0dc0a09235b49
Roller-URL: https://ci.chromium.org/b/8811250052372404545
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811250052372404545
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2f52cce9a4366cbecb3ead5b3702db61b9a5b23c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/98235
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 4331b17..3f0dc0a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 4331b174c459809439130c84bf12a26d78df7180
+Subproject commit 3f0dc0a09235b49d2e7fdfbca99e644ff2b2fd4b