Sync with upstream NetBSD lib/libc/regex.

Bug: http://b/22850181
Change-Id: I11a51a2031e68a953ccd5691da98c699c7d01904

(cherry-picked from commit 71927a82379f7a72559ea96e6678d6215090937f)
diff --git a/libc/upstream-netbsd/android/include/netbsd-compat.h b/libc/upstream-netbsd/android/include/netbsd-compat.h
index 84be931..f61e90a 100644
--- a/libc/upstream-netbsd/android/include/netbsd-compat.h
+++ b/libc/upstream-netbsd/android/include/netbsd-compat.h
@@ -31,4 +31,7 @@
 #define __readlockenv() 0
 #define __unlockenv() 0
 
+#include <stddef.h>
+__LIBC_HIDDEN__ int reallocarr(void*, size_t, size_t);
+
 #endif