Fix mips strace build.

Change-Id: I291380149d22282a12ec1def81da3f65330ceeb5
diff --git a/sys_func.h b/sys_func.h
index 51fb1ef..c040a58 100644
--- a/sys_func.h
+++ b/sys_func.h
@@ -264,6 +264,7 @@
 extern SYS_FUNC(symlinkat);
 extern SYS_FUNC(sync_file_range);
 extern SYS_FUNC(sync_file_range2);
+extern SYS_FUNC(syscall);
 extern SYS_FUNC(sysctl);
 extern SYS_FUNC(sysinfo);
 extern SYS_FUNC(syslog);