Disables systemd-timesyncd to stop RTC changing

Masks out the systemd-timesyncd service, which provides Network Time Protocol
time synchronization because it modifies the hardware clock (also known as the
RTC) even with `hwclock --hctosys` being set at boot.

There's no simple way around modifying the hardware clock whenever the Linux
kernel synchronizes time: it happens within the kernel and the only way to
change this behavior is use a kernel compiled with a certain flag, which is not
feasible at this stage due to Secure Boot considerations.

[1] rescuezilla#107

chroot.steps.part.1.sh

@@ -234,3 +234,11 @@ rm /usr/share/icons/*/icon-theme.cache
 rm -rf /usr/share/doc
 rm -rf /usr/share/man
 rm -rf /etc/network/if-up.d/ntpdate
+
+# Disable systemd's built-in NTP time synchronization service by manually masking it (`systemctl mask`)
+# using a symlink. This timesyncd service always modifies the hardware clock, and there
+# does not appear to be a way to prevent this service from modifying the hardware clock.
+# See [1] for more discussion.
+# [1] https://github.com/rescuezilla/rescuezilla/issues/107
+rm /etc/systemd/system/systemd-timesyncd.service
+ln -s /dev/null /etc/systemd/system/systemd-timesyncd.service