[third_party/pigweed] Roll 2 commits

ece72da0c2594b4 roll: clang
ed6838928252163 pw_unit_test: Use googletest backend as a dep

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 869da39148d3373..ece72da0c2594b4
Roller-URL: https://ci.chromium.org/b/8761965238240706465
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I56b4dd773c2d4bf894dc1c2fb75a3482de7539e2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/184660
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 869da39..ece72da 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 869da39148d337306eae1ce0ec365aa1abb9d818
+Subproject commit ece72da0c2594b41199dcc4e65d0e026e28e146c