Add callback to lumo.build.api/build

This change was made necessary by the fact that the bootstrap compiler is
asynchronous by default. Therefore, it does not make sense to call
lumo.build.api/build without a callback.

The patch does not break old code, so it still contains the arity without cb,
but includes a warning if that arity is invoked.

src/cljs/bundled/lumo/build/api.cljs

@@ -37,15 +37,19 @@
 (defn build
   "Given a source which can be compiled, produce runnable JavaScript."
   ([source opts]
-   (build source opts
-     (env/default-compiler-env
-       (closure/add-externs-sources opts))))
+   (build source opts (fn [& args] args)))
   ([source opts compiler-env]
+   (build source opts compiler-env cb))
+  ([source opts compiler-env cb]
    (doseq [[unknown-opt suggested-opt] (util/unknown-opts (set (keys opts)) closure/known-opts)]
      (when suggested-opt
        (println (str "WARNING: Unknown compiler option '" unknown-opt "'. Did you mean '" suggested-opt "'?"))))
    (binding [ana/*cljs-warning-handlers* (:warning-handlers opts ana/*cljs-warning-handlers*)]
-     (closure/build source opts compiler-env))))
+     (closure/build source opts
+                    (if compiler-env
+                      compiler-env
+                      (env/default-compiler-env
+                       (closure/add-externs-sources opts))) cb))))
 
 (defn inputs
   "Given a list of directories and files, return a compilable object that may

src/cljs/bundled/lumo/closure.cljs

@@ -2153,17 +2153,16 @@
 
 (defn build
   "Given a source which can be compiled, produce runnable JavaScript."
-  ([source opts]
+  ([source opts cb]
    (build source opts
       (if-not (nil? env/*compiler*)
         env/*compiler*
         (env/default-compiler-env
           ;; need to dissoc :foreign-libs since we won't know what overriding
           ;; foreign libspecs are referring to until after add-implicit-options
           ;; - David
-          (add-externs-sources (dissoc opts :foreign-libs))))))
-  ([source opts compiler-env]
-   (build source opts compiler-env (fn [& args] args)))
+          (add-externs-sources (dissoc opts :foreign-libs))))
+      cb))
   ([source opts compiler-env cb]
    (env/with-compiler-env compiler-env
      ;; we want to warn about NPM dep conflicts before installing the modules