roll: third_party/pigweed bazel: Propagate pigweed_json flag to exec config

Tools running in the exec configuration (like the docs build) will
generally require this flag to be set.

Fixes: 390456900
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/261738
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: afeddbb2b6e2aed9deed36db168e877f9d8b6a30

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 846fbf52a8b848..afeddbb2b6e2ae
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8725067010146769377
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia674d0e1d4676960441f5063353a1c382bd5ac33
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/261637
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 846fbf5..afeddbb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 846fbf52a8b8487c51d55c057a92038559347e02
+Subproject commit afeddbb2b6e2aed9deed36db168e877f9d8b6a30