Add gitiles project

This adds the gitiles project to the check pipeline without any
jobs.  We can add the jobs in the gitiles repo.

Change-Id: I98cf91390b98c9415171b8f7fc928fc8e8f4ee94
diff --git a/zuul.d/projects.yaml b/zuul.d/projects.yaml
index 0b74d64..c39539c 100644
--- a/zuul.d/projects.yaml
+++ b/zuul.d/projects.yaml
@@ -293,3 +293,12 @@
     name: plugins/zuul-results-summary
     templates:
       - non-core-plugin
+
+# Other projects
+
+# Attach the gitiles project to the check pipeline, but defer to
+# gitiles in-repo config for jobs.
+- project:
+    name: gitiles
+    check:
+      jobs: []