Build gitiles plugin on Gerrit v2.15

Change-Id: I1a26b208dc7c91944fe60a6bf9e6e639aa1f92bf
diff --git a/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml b/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
index 2cc61b5..b826245 100644
--- a/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
@@ -15,5 +15,10 @@
             - stable-2.10
       - 'plugin-{name}-bazel-{branch}':
           branch:
-            - master
             - stable-2.14
+      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
+          branch:
+            - master
+          gerrit-branch:
+            - master
+            - stable-2.15