[pigweed] Roll 2 commits

6638f775a941120 third_party/fuchsia: Fix preprocessor check
a5062524d71e4f8 pw_toolchain: Add basic (and incomplete) Rust tool

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: 80ed1db4b1dae63..6638f775a941120
Roller-URL: https://ci.chromium.org/b/8806714093073585185
Cq-Cl-Tag: roller-builder:pigweed-zephyr-roller
Cq-Cl-Tag: roller-bid:8806714093073585185
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1b2ad29058471f1f2b6b7a4b06cd0e64a46af6be
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/105012
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/pigweed b/pigweed
index 80ed1db..6638f77 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit 80ed1db4b1dae6377a976a21e756a2f77764dd8a
+Subproject commit 6638f775a94112069d4c7a9df5c3e094622cd605