[roll third_party/pigweed] third_party: Add third_party/Emboss

Add emboss_cc_library GN template for compiling Emboss source files
and instructions on how to add Emboss as a submodule. See docs.rst
for more info.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/124392

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 651e2bc3cae77d2..a9daf080ac96f3d
Roller-URL: https://ci.chromium.org/b/8792311250410233201
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id9232f92d9dd226bd58e60d3613b7f55bf9de216
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/126349
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 651e2bc..a9daf08 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 651e2bc3cae77d25bf039b9448192bf31ce4c34b
+Subproject commit a9daf080ac96f3dc7d585afea91e31dc94271144