Run PolyGerrit tests when WORKSPACE is changed

Updating the Bazel WORKSPACE file can have a ripple effect
on the stability of the PolyGerrit build.

Make sure that PolyGerrit tests are run every time that
the WORKSPACE file is changed.

Change-Id: I9e477c9d9956c8a42ed02e9e6e1598dfda850df9
diff --git a/jenkins/gerrit-verifier-change.groovy b/jenkins/gerrit-verifier-change.groovy
index befb351..6fa43b8 100644
--- a/jenkins/gerrit-verifier-change.groovy
+++ b/jenkins/gerrit-verifier-change.groovy
@@ -320,7 +320,7 @@
     def changedFiles = gerrit.getChangedFiles(changeNum, sha1)
     def polygerritFiles = changedFiles.findAll { it.startsWith("polygerrit-ui") }
 
-    if(polygerritFiles.size() > 0) {
+    if(polygerritFiles.size() > 0 || changedFiles.contains("WORKSPACE")) {
       if(changedFiles.size() == polygerritFiles.size()) {
         println "Only PolyGerrit UI changes detected, skipping other test modes..."
         modes = ["polygerrit"]