Nullability check for time module.

Bug: b/245972273
Test: adb shell
Change-Id: I61f69f48f3428ef1f544dd01e573ff078a9eab17
diff --git a/libc/include/sys/times.h b/libc/include/sys/times.h
index 25d03e3..8b6e91d 100644
--- a/libc/include/sys/times.h
+++ b/libc/include/sys/times.h
@@ -46,6 +46,6 @@
  * Returns a (possibly overflowed) absolute time on success,
  * and returns -1 and sets `errno` on failure.
  */
-clock_t times(struct tms* __buf);
+clock_t times(struct tms* _Nullable __buf);
 
 __END_DECLS