[roll pigweed] pw_env_setup: Don't assume lib2to3 lib dir exists

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/100462

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: e22c6ffa2374ee9..f6df36c81ed3669
Roller-URL: https://ci.chromium.org/b/8809980375165277377
Cq-Cl-Tag: roller-builder:pigweed-zephyr-roller
Cq-Cl-Tag: roller-bid:8809980375165277377
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia103843812cfaf73e295b7c76d7e2216dd843f56
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/100437
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/pigweed b/pigweed
index e22c6ff..f6df36c 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit e22c6ffa2374ee987ab0bcbf8fd7af0f7e7186c6
+Subproject commit f6df36c81ed3669a100336e4af5ce8be247d8518