Clean Workspace Before Build: This option will cause the plugin to delete all files in the workspace before running a build.
This option will also cause the plugin to perform a force sync to retrieve clean files from the perforce server.
This option can also be triggered by creating a boolean parameter on the build called "P4CLEANWORKSPACE".
Important Note: It is highly recommended that you enable this or the 'Always Force Sync' option when using a Matrix or Multiconfiguration build. Failing to do so could cause child builds to not be synced properly.