When a system has a wrong date and time timesyncd is unable to synchronize it
because DNSSEC doesn't work. In order to break this chicken and egg problem
systemd-timesync disables DNSSEC validation by setting
SYSTEMD_NSS_RESOLVE_VALIDATE=0 in the unit file. However, it doesn't work in
NixOS because it uses NSCD. This patch disables NSCD in systemd-timesyncd when
SYSTEMD_NSS_RESOLVE_VALIDATE is set to 0 so that it uses NSS libraries
directly. In order for it to be able to find the libnss_resolve.so.2 library
this patch adds the systemd directory in the nix store to the LD_LIBRARY_PATH.
