wait-time-sync: new package to reliable detect ntp synchronized system time

packages/sysutils/wait-time-sync/package.mk

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+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020-present Team LibreELEC (https://libreelec.tv)
+
+PKG_NAME="wait-time-sync"
+PKG_VERSION="1.0"
+PKG_LICENSE="GPL"
+PKG_SITE=""
+PKG_URL=""
+PKG_DEPENDS_TARGET="toolchain"
+PKG_LONGDESC="A simple tool and systemd service to wait until NTP time is synced"
+
+
+post_install() {
+  enable_service wait-time-sync.service
+}

packages/sysutils/wait-time-sync/sources/Makefile

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+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020-present Team LibreELEC (https://libreelec.tv)
+
+.PHONY: all
+all: wait-time-sync
+
+PREFIX = /usr
+
+.PHONY: install
+install: wait-time-sync
+	install -d $(DESTDIR)$(PREFIX)/bin
+	install $< $(DESTDIR)$(PREFIX)/bin

packages/sysutils/wait-time-sync/sources/wait-time-sync.c

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+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020-present Team LibreELEC (https://libreelec.tv) */
+
+#include <sys/timex.h>
+#include <unistd.h>
+#include <errno.h>
+
+int main()
+{
+  int rc;
+
+  for (;;)
+  {
+    struct timex tx = {};
+
+    rc = adjtimex(&tx);
+    if (rc != TIME_ERROR)
+      break;
+    usleep(1000000U/3);
+  }
+
+  return rc == -1 ? errno : 0;
+}

packages/sysutils/wait-time-sync/system.d/wait-time-sync.service

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+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  This file was part of systemd.
+#  Modified by Team LibreELEC (https://libreelec.tv)
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Wait For Kernel Time Synchronized
+
+ConditionVirtualization=!container
+
+DefaultDependencies=no
+Before=time-sync.target shutdown.target
+Wants=time-sync.target
+Conflicts=shutdown.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/wait-time-sync
+TimeoutStartSec=infinity
+RemainAfterExit=yes
+
+[Install]
+WantedBy=sysinit.target