Make Zuul's environment available to shell jobs

The idea is to use `jq` locallty to extract whatever is relevant for
these jobs.

Change-Id: I4a549241016b20dab4338fea363cba266bdd38a8
diff --git a/playbooks/zuul-var-to-json/run.yaml b/playbooks/zuul-var-to-json/run.yaml
new file mode 100644
index 0000000..6c97ecf
--- /dev/null
+++ b/playbooks/zuul-var-to-json/run.yaml
@@ -0,0 +1,6 @@
+- hosts: all
+  tasks:
+    - name: Export Zuul variables into JSON
+      copy:
+        dest: '{{ ansible_user_dir }}/zuul-env.json'
+        content: '{{ zuul | to_json }}'