roll: third_party/pigweed pw_rpc2: Set MallocNanoZone=0 on macOS for echo_test

Under macOS sanitizers (such as AddressSanitizer), the sanitizer runtime
reserves virtual memory early during startup, preventing macOS's nano
malloc zone from reserving its fixed address range and causing libmalloc
to log:

  malloc: nano zone abandoned due to inability to reserve vm space.

Because echo_test captures combined output from the example client and
server processes and compares it against expected output files, this
warning interrupts the expected echo logs and causes the test to fail.
Set MallocNanoZone=0 on macOS to disable nano zone initialization.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/500413
Original-Revision: 802a7cbb62b4cd48d1085541df2e30b899f31d64

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 8e2d22c29c2956..802a7cbb62b4cd
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8668164131596066641
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I333d6a3a768f2676413821f0f58bf5da6eadfaf3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/500593
diff --git a/third_party/pigweed b/third_party/pigweed
index 8e2d22c..802a7cb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 8e2d22c29c2956d28a9f077203d74197d1722fd0
+Subproject commit 802a7cbb62b4cd48d1085541df2e30b899f31d64