traced_relay: add tests for the relay service

Bug: 284258446
Change-Id: Ibd9dd3c86d4dc05c1722633865c81cb0ee904eb3
diff --git a/gn/perfetto_unittests.gni b/gn/perfetto_unittests.gni
index cc51910..91e8d5d 100644
--- a/gn/perfetto_unittests.gni
+++ b/gn/perfetto_unittests.gni
@@ -80,3 +80,7 @@
     perfetto_unittests_targets += [ "src/bigtrace:unittests" ]
   }
 }
+
+if (enable_perfetto_traced_relay) {
+  perfetto_unittests_targets += [ "src/traced_relay:unittests" ]
+}