Fix mac build
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dbc2b4b..c521b79 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3106,6 +3106,7 @@
 if (gRPC_BUILD_TESTS)
 
 add_library(grpc_benchmark
+  test/cpp/microbenchmarks/helpers.cc
 )
 
 if(WIN32 AND MSVC)