[roll third_party/pigweed] pw_software_update: Sign a bundle via CLI

Add functionality for signing of bundle

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/120671

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 23304eb9d53978c..85b5cd9d9b3375c
Roller-URL: https://ci.chromium.org/b/8796845874470573537
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie19d25fcbc3bd39d975bd429b46b26db9e70c66a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/120691
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 23304eb..85b5cd9 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 23304eb9d53978c956a52e87aff6b49cb9c8607a
+Subproject commit 85b5cd9d9b3375c41eb52c027b80d764472173e9