[roll third_party/pigweed] bazel: Rename BUILD to BUILD.bazel

Avoids potential naming conflicts with other build systems.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/49306

third_party/pigweed Rolled-Commits: 16541e7699118f3..40a9c3f128f6a27
Roller-URL: https://ci.chromium.org/b/8841703545990286272
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8841703545990286272
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I45cfae4e38d36a528a77638d327c133dc7511856
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/53081
Reviewed-by: 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 16541e7..40a9c3f 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 16541e7699118f38b31f8dcd64cbfabe8d72c277
+Subproject commit 40a9c3f128f6a279d6aee6aef45705725689189a