[roll third_party/pigweed] pw_toolchain: For bazel rust toolchains, allow specifying constraints

To support arbitrary constraints on the generated rust toolchain, pass
extra list to append to target_compatible_with on the toolchain.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/150030

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9145e954fb635e3..4e79a2ec4cc639c
Roller-URL: https://ci.chromium.org/b/8779455093980310481
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Idf20a26118824710faa780c615b0f1a8be96942a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/150091
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 9145e95..4e79a2e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9145e954fb635e3f25a5240342bd42589e7f551c
+Subproject commit 4e79a2ec4cc639cd5fada6084216e5586acf4bdd