Add faccessat to syscall list

Change-Id: I427a18811089cb280769ac8da3ed8adc00a65a10
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index d92549f..d8263fe 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -107,6 +107,7 @@
 #define F_OK  0  /* Existence */
 
 extern int access(const char *, int);
+extern int faccessat(int, const char *, int, int);
 extern int link(const char *, const char *);
 extern int unlink(const char *);
 extern int chdir(const char *);