It was failing with a `Read-only filesystem` failure due to the systemd
service option `ReadWriteDirectories` not being correctly configured.
Fixes#14132
(cherry picked from commit f5951c55f7)
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
