[roll third_party/pigweed] pw_libcxx: Minimal implementation

Provide a minimal pw_libcxx implementation that uses LLVM libc++.

Bugs: https://pwbug.dev/298822102
Docs: N/A
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/201918
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 188876aa96f12be..258066a475ea2cf
Roller-URL: https://ci.chromium.org/b/8748519156472606337
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie763cefdff9ca29d107cde80e9e2e11bbaee38c7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/208991
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 188876a..258066a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 188876aa96f12bebe1a1e38989f339a50fcb83b2
+Subproject commit 258066a475ea2cfb2a39138c05f179706896457e