[roll third_party/pigweed] pw_toolchain_bazel: Add support for setting environment variables

Original-Bug: 322872628
Test: bazel build //cc_toolchain/test/...
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/190154

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 221456bd12cd382..65866c3bb3d44a3
Roller-URL: https://ci.chromium.org/b/8756608932366832657
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ief0e8213c3a0a047e381a6566910366f025c25fe
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/190993
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.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 221456b..65866c3 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 221456bd12cd382ad5e3db4f67bd1892174714f0
+Subproject commit 65866c3bb3d44a350f45f2d5da17f2899cf2dcad