Remove everything from target before copying new Hugo output

Signed-off-by: Mikaël Barbero <mikael.barbero@eclipse-foundation.org>
diff --git a/Jenkinsfile b/Jenkinsfile
index b9517ce..110ff49 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -87,7 +87,7 @@
         }
       }
       steps {
-        sh 'cp -Rvf hugo/public/* www/'
+        sh 'rm -rf www/* && cp -Rvf hugo/public/* www/'
         dir('www') {
             sshagent(['git.eclipse.org-bot-ssh']) {
                 sh '''
@@ -108,4 +108,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}