feat: Use timesyncd with recovery clock file

Replaced ntpd with sytemd timesyncd. This allows to use a recovery clock
file to have a more accurate system time during boot up.
This greatly helps with log file timestamps. Otherwise they always start
in 2019 and journal logs get all messed up until time synchronization is
available.

The recovery clock file is updated 2min after boot up, thereafter every
5 minutes and before shutdown. Whenever timesyncd receives a time update
the file is updated as well internally by timesyncd.

More information: https://wiki.archlinux.org/index.php/Systemd-timesyncd

overlay/etc/systemd/system/multi-user.target.wants/shutdown-clock-file.service

@@ -0,0 +1 @@
+../shutdown-clock-file.service

overlay/etc/systemd/system/multi-user.target.wants/update-clock-file.timer

@@ -0,0 +1 @@
+../update-clock-file.timer

overlay/etc/systemd/system/shutdown-clock-file.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Final clock file update before shutdown
+RequiresMountsFor=/
+
+[Service]
+ExecStop=/etc/update_clock_file.sh
+Type=oneshot
+RemainAfterExit=yes
+
+[Install]
+WantedBy=multi-user.target

overlay/etc/systemd/system/update-clock-file.service

@@ -0,0 +1,9 @@
+
+[Unit]
+Description=Run clock file update script
+RefuseManualStart=no
+RefuseManualStop=no
+
+[Service]
+Type=oneshot
+ExecStart=/etc/update_clock_file.sh

overlay/etc/systemd/system/update-clock-file.timer

@@ -0,0 +1,9 @@
+[Unit]
+Description=Clock file update timer
+
+[Timer]
+OnBootSec=120
+OnUnitActiveSec=300
+
+[Install]
+WantedBy=multi-user.target

overlay/etc/update_clock_file.sh

@@ -0,0 +1,2 @@
+#! /usr/bin/env sh
+touch /var/lib/systemd/timesync/clock

overlay/opt/yio/scripts/firstrun.sh

@@ -8,7 +8,6 @@ then
     #--------------------
     # Do some setup with services
     #--------------------
-    systemctl disable systemd-timesyncd.service
     systemctl disable dhcpcd.service
     systemctl disable lighttpd.service
 

rpi0/defconfig

@@ -94,6 +94,7 @@ BR2_PACKAGE_IW=y
 BR2_PACKAGE_LIGHTTPD=y
 BR2_PACKAGE_LIGHTTPD_PCRE=y
 BR2_PACKAGE_NTP=y
+# BR2_PACKAGE_NTP_NTPD is not set
 BR2_PACKAGE_WPA_SUPPLICANT=y
 BR2_PACKAGE_WPA_SUPPLICANT_AP_SUPPORT=y
 BR2_PACKAGE_WPA_SUPPLICANT_WIFI_DISPLAY=y
@@ -105,7 +106,6 @@ BR2_PACKAGE_BASH=y
 # BR2_PACKAGE_SYSTEMD_HWDB is not set
 # BR2_PACKAGE_SYSTEMD_MYHOSTNAME is not set
 BR2_PACKAGE_SYSTEMD_RFKILL=y
-# BR2_PACKAGE_SYSTEMD_TIMESYNCD is not set
 BR2_PACKAGE_UTIL_LINUX_KILL=y
 BR2_PACKAGE_UTIL_LINUX_RFKILL=y
 BR2_PACKAGE_NANO=y