roll: third_party/pigweed pw_toolchain: Add migration shim for legacy GCC toolchain rules

Original-Bug: b/346388161
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/247872
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: dea7775e165fcd6c03143b3b2000cd5c69493643

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: e4fe3eb3c811aa..dea7775e165fcd
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8731545796936405249
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I4a3772c86df2c53f9bfc4b45e37b886822b266e7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/248093
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.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 e4fe3eb..dea7775 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit e4fe3eb3c811aaca1ce97ebe298340864bc01c9f
+Subproject commit dea7775e165fcd6c03143b3b2000cd5c69493643