[roll third_party/pigweed] pw_system: Add pw_malloc facade when using Linux

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/78280

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 09a2f4c76a4a096..02e20c8728b9aeb
Roller-URL: https://ci.chromium.org/b/8825217088529552801
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8825217088529552801
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ic034f1ed42d8e36859f1f0d67b3cb52c1e1840ed
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/78300
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 09a2f4c..02e20c8 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 09a2f4c76a4a096a80465de590c7fddc2bf52746
+Subproject commit 02e20c8728b9aeb07f2abbf07cbf4bc644a8da34