More work on seccomp for Arch #633

I think the root of the issue is an ommision in
  /usr/include/seccomp-syscalls.h
Fedora seems fixed.  The same issue has poped up on Alpine Linux.
Editing the above header file fixed it.

ntpd/ntp_sandbox.c

@@ -416,9 +416,10 @@ int scmp_sc[] = {
 /* But somebody switched to SNR vs NR so we need a way
  * to test for old/new so we can do the right ifdef. */
 // Currently broken on Arch Linux but passes GitLab CI
-// #ifdef __NR_ppoll
-//	SCMP_SYS(ppoll),
-// #endif
+#ifdef __NR_ppoll
+	SCMP_SYS(ppoll),
+	SCMP_SYS(clock_adjtime),
+#endif
 	SCMP_SYS(sendmsg),
 #ifdef __NR_geteuid32
 	SCMP_SYS(geteuid32),