Merge pull request #18632 from yashykt/backport_cfstreamfix

backport #18606 - Add a dummy function to grpc cfstream library

src/core/lib/iomgr/cfstream_handle.cc

@@ -192,4 +192,11 @@ void CFStreamHandle::Unref(const char* file, int line, const char* reason) {
   }
 }
 
+#else
+
+/* Creating a dummy function so that the grpc_cfstream library will be
+ * non-empty.
+ */
+void CFStreamDummy() {}
+
 #endif