Start hiding "private/bionic_time.h".

Bug: 15765976
Change-Id: Ibd9cf07067ec8dffe9fda6c3d498d4ab90708220
diff --git a/libc/include/sys/cdefs_elf.h b/libc/include/sys/cdefs_elf.h
index b5db13e..4dd7dc3 100644
--- a/libc/include/sys/cdefs_elf.h
+++ b/libc/include/sys/cdefs_elf.h
@@ -68,7 +68,7 @@
 #ifdef __LP64__
 #define __LIBC64_HIDDEN__ __LIBC_HIDDEN__
 #else
-#define __LIBC64_HIDDEN__
+#define __LIBC64_HIDDEN__ __LIBC_ABI_PUBLIC__
 #endif
 
 /* Used to tag non-static symbols that are public and exposed by the shared library. */