Add missing libc++ includes

Bug: 175635923
Test: m MODULES-IN-frameworks-native-libs-binder
Change-Id: I43d3b767ad0878c828abdc5c1a35197cb46a2d75
diff --git a/libs/binder/UtilsHost.h b/libs/binder/UtilsHost.h
index b582f17..d6fe9fa 100644
--- a/libs/binder/UtilsHost.h
+++ b/libs/binder/UtilsHost.h
@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <functional>
 #include <optional>
 #include <ostream>
 #include <string>