Add build-site job

Add a Zuul job to build the site and publish a test version to the
log server.

Change-Id: I364d7576973f68d991dbb3a4dafc189cf94192f6

.zuul.yaml

@@ -1,3 +1,16 @@
+- job:
+    name: netlify-sandbox-build-site
+    parent: build-javascript-content
+    success-url: "site/.vuepress/dist"
+    vars:
+      javascript_content_dir: "site/.vuepress/dist"
+      node_version: 8
+    run: playbooks/build-site/run.yaml
+
 - project:
-    templates:
-      - noop-jobs
+    check:
+      jobs:
+        - netlify-sandbox-build-site
+    gate:
+      jobs:
+        - netlify-sandbox-build-site

playbooks/build-site/run.yaml

@@ -0,0 +1,5 @@
+- hosts: all
+  roles:
+    - revoke-sudo
+    - role: yarn
+      yarn_command: site:build