Upstream atexit

Change-Id: Ia454a2181b5058ed9783dc02b6b1805d0e4d2715
diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h
index f00d91a..cf63907 100644
--- a/libc/upstream-openbsd/android/include/openbsd-compat.h
+++ b/libc/upstream-openbsd/android/include/openbsd-compat.h
@@ -40,4 +40,6 @@
 __LIBC64_HIDDEN__ extern const short *_tolower_tab_;
 __LIBC64_HIDDEN__ extern const short *_toupper_tab_;
 
+__LIBC_HIDDEN__ extern struct atexit *__atexit;
+
 #endif