Update prebuilts for RS compat lib.

Change-Id: Ieb867f63b27792d1c309952e9d86bc719bfadcd3
diff --git a/renderscript/clang-include/stdalign.h b/renderscript/clang-include/stdalign.h
index e7fbfa0..3738d12 100644
--- a/renderscript/clang-include/stdalign.h
+++ b/renderscript/clang-include/stdalign.h
@@ -24,7 +24,12 @@
 #ifndef __STDALIGN_H
 #define __STDALIGN_H
 
+#ifndef __cplusplus
 #define alignas _Alignas
+#define alignof _Alignof
+#endif
+
 #define __alignas_is_defined 1
+#define __alignof_is_defined 1
 
 #endif /* __STDALIGN_H */