Build COMPARISON_BRANCH variable for checking chart versions

Change-Id: Ib97558156c62e9c458a57c338a6144734bd72901
diff --git a/jjb/lint.yaml b/jjb/lint.yaml
index d7bdaf4..b9ac176 100644
--- a/jjb/lint.yaml
+++ b/jjb/lint.yaml
@@ -137,6 +137,9 @@
 
           git clone https://gerrit.opencord.org/helm-repo-tools
           ./helm-repo-tools/helmlint.sh clean
+
+          # Specify the remote branch to compare against
+          export COMPARISON_BRANCH="origin/$GERRIT_BRANCH"
           ./helm-repo-tools/chart_version_check.sh