Remove duplicate entries from its-jira.jar

The inclusion of the Atlassian Jira REST API jar
generated the inclusion of duplicates LICENSE.txt files
in the jar. That generated a waterfall effect on the inability
to correctly update the manifest with the version info.

Change-Id: Id992e41e0c5a1ead1872f07b57913241e8a68ea0
diff --git a/jenkins/gerrit-buck-build-its-plugin.sh b/jenkins/gerrit-buck-build-its-plugin.sh
index d4b6c77..fe0cd58 100644
--- a/jenkins/gerrit-buck-build-its-plugin.sh
+++ b/jenkins/gerrit-buck-build-its-plugin.sh
@@ -20,8 +20,13 @@
 
 buck build -v 3 plugins/its-{name}
 
+# Remove duplicate entries
+PLUGIN_JAR=$(ls $(pwd)/buck-out/gen/plugins/its-{name}/its-{name}*.jar)
+mkdir jar-out && pushd jar-out
+jar xf $PLUGIN_JAR && jar cmf META-INF/MANIFEST.MF $PLUGIN_JAR .
+popd
+
 # Extract version information
-PLUGIN_JAR=$(ls buck-out/gen/plugins/its-{name}/its-{name}*.jar)
 PLUGIN_VERSION=$(git describe --always origin/{branch})
 echo -e "Implementation-Version: $PLUGIN_VERSION" > MANIFEST.MF
 jar ufm $PLUGIN_JAR MANIFEST.MF && rm MANIFEST.MF