[roll third_party/pigweed] pw_toolchain: Add missing {{arflags} to tool("alink")

GN configs support flags for ar. Typically it is used to enable thin
archives. Allow this in pigweed.

No-Docs-Update-Reason: We're not documenting GN here.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39440

third_party/pigweed Rolled-Commits: 5ea3340c283bc59..f47febb0da2dd27
Roller-URL: https://ci.chromium.org/b/8851119076112481072
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8851119076112481072
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7250df00f0adfc392234f536d4c507b92a501200
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/39761
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 5ea3340..f47febb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5ea3340c283bc59773ea1ef7f1810faa2f2c9655
+Subproject commit f47febb0da2dd27118d3c8134b957cb79fc5f26f