Release process: clock the IUK generation process

wiki/src/contribute/release_process.mdwn

@@ -944,6 +944,7 @@ before starting the wrapper from `puppet-tails`:
        cd "${WORK_DIR?:}"
        git clone "$PUPPET_TAILS_REMOTE"
        sudo -l
+       time                                                                   \
        ./puppet-tails/files/jenkins/slaves/isobuilders/wrap_tails_create_iuks \
            --tails-git-remote "file://${RELEASE_CHECKOUT?:}/.git"             \
            --tails-git-commit "${TAG?:}"                                      \