[roll third_party/pigweed] pw_build: Relative source file name extraction

Adds a helper template that can extract source file names from pw_*
build targets as represented by the __FILE__ macro with
-ffile-prefix-map transformations applied.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/79540

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 0981b304dd32084..a72272bf9e31236
Roller-URL: https://ci.chromium.org/b/8824544976912741953
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8824544976912741953
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I54f1c628d07f6a3df3dc4333444690fa810bf7ad
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/79801
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 0981b30..a72272b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 0981b304dd32084f118e90c0a53a2c837dbf7902
+Subproject commit a72272bf9e312364bd088d773dbe22a0c443068d