roll: third_party/pigweed 4 commits

95951f4f88891c1 bazel: Modernize pip deps style
9c64c8d1cd1cec4 pw_cpu_exception_cortex_m: Make PC LR optional
a98647d744dc24c pw_toolchain: Add linux_sysroot.bzl
7dc26abc274fa80 pw_libcxx: Actually implement operator delete

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b2afd53cde2dcc9..95951f4f88891c1
Roller-URL: https://ci.chromium.org/b/8742137042828238433
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ibca74313c3e0df2d5bc39089597dc175d842bbcb
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/223798
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index b2afd53..95951f4 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b2afd53cde2dcc9a9b906bde613513ea5f6e9f6b
+Subproject commit 95951f4f88891c15be94a57bf2773d3441d404c3