[roll third_party/pigweed] pw_toolchain: Make tools use relative paths

Changes GN toolchains to use relative paths to tools by default rather
than relying on the system PATH.

Original-Bug: b/290848929
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/159130

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: f04f934b3c69910..0889de69c640669
Roller-URL: https://ci.chromium.org/b/8774572406234406049
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7e5feb8b2de703da0606b530aec4496f94728253
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/159271
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 f04f934..0889de6 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f04f934b3c69910f866059471625a2bc95e113c4
+Subproject commit 0889de69c640669e2582da4735ca54c432806113