Add "target_suffix" to gerrit_plugin()
Add "target_suffix" to gerrit_plugin()

The "target_suffix" parameter is added to the gerrit_plugin()
definition as a way to facilitate a custom "post-build" type of
step, such as with the Gitiles plugin, where the additional static
files need to be moved into the root of the JAR file.

Change-Id: I44ea892377c0099f6fada7fa77e3945bc9df3bfd

gerrit-review/gerrit,renchaorevee/gerrit,joshuawilson/merrit,joshuawilson/merrit,MerritCR/merrit,GerritCodeReview/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,MerritCR/merrit,joshuawilson/merrit,gerrit-review/gerrit,renchaorevee/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,renchaorevee/gerrit,renchaorevee/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,joshuawilson/merrit,renchaorevee/gerrit,WANdisco/gerrit,MerritCR/merrit,joshuawilson/merrit,MerritCR/merrit,MerritCR/merrit,GerritCodeReview/gerrit,renchaorevee/gerrit,GerritCodeReview/gerrit,renchaorevee/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,joshuawilson/merrit,gerrit-review/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,joshuawilson/merrit,joshuawilson/merrit,gerrit-review/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit