flink.clj

(deflinked abclink [a b c])

;; expands to

(defn abclink [params]
  (let [[to] (when-let [t (:to params)] (clojure.tools.build.api/qualify-fn-symbols [t]))]
    (loop [parms params
           remaining-tasks [build/a build/b build/c]]
      (let [task (first remaining-tasks)]
        (if task
          (let [ret (task parms)]
            (if (and to (= to task))
              ret
              (recur ret (rest remaining-tasks))))
          parms)))))

;; called as

clj -X:build abclink ;; performs tasks a,b,c

;; or 

clj -X:build abclink :to b ;; performs tasks a,b