[roll third_party/pigweed] pw_toolchain: Link against system libraries using libs not ldflags

Original-Fixed: b/285357895
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/151050

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5382e92723657bf..6a8e03c80c84522
Roller-URL: https://ci.chromium.org/b/8771856413533492945
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I6e3a078dd421f1ce33124fa957802a4174df2da2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/168492
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 5382e92..6a8e03c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5382e92723657bf4c92eb4379e820d8e8512918b
+Subproject commit 6a8e03c80c8452247c3d987d6a06f0c0b39acf57