Without this the journal will be filled by
xscreensaver[468297]: sh: line 1: xscreensaver-command: command not found
xscreensaver-systemd: 12:29:22: exec: "xscreensaver-command -quiet -deactivate" exited with status 127
Before, loading a module would be guarded by an optional platform
condition. This made it possible to avoid loading and evaluating a
module if it did not support the host platform.
Unfortunately, this made it impossible to share a single configuration
between GNU/Linux and Darwin hosts, which some wish to do.
This removes the conditional load and instead inserts host platform
assertions in the modules that are platform specific.
Fixes#1906
