Add enable_systemd variable

playbooks/LinuxCLI.yaml

@@ -13,3 +13,4 @@
     - role: gdb
     - role: podman
     - role: system-info
+      when: enable_systemd

playbooks/vars/environment.yaml

@@ -1,4 +1,7 @@
 ---
+# (Dis/en)able usage of systemd units.
+enable_systemd: '{{ ansible_env.enable_systemd | default(True) }}'
+
 # GitHub may rate limit unauthenticated API requests, this is more likely when
 # behind a network proxy. Set the GITHUB_TOKEN environment variable to
 # authenticate any GitHub API requests executed while playing roles.