It turns out I missed an indirect dependency after all in 1244
diff --git a/build.json b/build.json
index ada3e0e..8e454d7 100644
--- a/build.json
+++ b/build.json
@@ -548,6 +548,7 @@
       ],
       "deps": [
         "grpc++_test_util",
+        "grpc_test_util",
         "grpc++",
         "grpc",
         "gpr"