[roll third_party/pigweed] pw_presubmit: Merge GN args instead of appending

'gn gen' only processes the last '--args', so combine arguments from
multiple sources and then turn the result into a single '--args' option.

Original-Bug: b/264560441
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/126210

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 0aadffb405043a6..737a5278aed7d4e
Roller-URL: https://ci.chromium.org/b/8792773594280324993
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I47febb39c90a292775b6677f3ab73444e872f0f5
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/126200
Bot-Commit: 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 0aadffb..737a527 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 0aadffb405043a61876d8c1a41b9c0f7eb66efe0
+Subproject commit 737a5278aed7d4e8ba9eb29c019c0ed93bc8c845