Binder: Flattenable is no longer a hard dependency

Bug: 302723053
Test: mma
Change-Id: I0dddbd085b1999c3eb11577e6120ea422be4c10a
diff --git a/libs/binder/tests/binderLibTest.cpp b/libs/binder/tests/binderLibTest.cpp
index 341e9ce..659943a 100644
--- a/libs/binder/tests/binderLibTest.cpp
+++ b/libs/binder/tests/binderLibTest.cpp
@@ -40,6 +40,7 @@
 #include <binder/IServiceManager.h>
 #include <binder/RpcServer.h>
 #include <binder/RpcSession.h>
+#include <utils/Flattenable.h>
 
 #include <linux/sched.h>
 #include <sys/epoll.h>