[roll third_party/pigweed] lm3s6965evb_qemu: Fix clang build

Silences an unsupported warning in the lm3s6965evb_qemu clang build, and
then restores the build step to the tryjob so the clang ARM build is run
in CI/CQ again.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/94582

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 3feef6a3514a2e8..72b7e34dea894e0
Roller-URL: https://ci.chromium.org/b/8814231130209461169
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8814231130209461169
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2afc1b6448b4206d2b47266cb678dac8a308d214
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/94603
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 3feef6a..72b7e34 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 3feef6a3514a2e818c50ebc4d4329622b15b54fb
+Subproject commit 72b7e34dea894e02cbd2193ce47b410c4db743ea