[roll third_party/pigweed] pw_unit_test: Add support for a test_main in CMake

Adds support to `pw_add_test` for a custom `test_main`. This is similar
to what we do for GN's `pw_test`.

Original-Fixes: 335865646

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/204872

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 188bd4726e0eca3..2d65e87e6086474
Roller-URL: https://ci.chromium.org/b/8749535042730970737
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9793131238079d7d01017e95fca54b905e9029f7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/206952
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 188bd47..2d65e87 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 188bd4726e0eca3c7cad7fa8f7c8b76c1e12cc38
+Subproject commit 2d65e87e608647405788400aad243b94010cf132