Proof of concept for babashka#50

Test with 
```
bb bbin install io.github.borkdude/carve --as carve-dev && cat $(which carve-dev) && carve-dev ; time carve-dev
```

0.069

Vs 

bbin install io.github.borkdude/carve --as carve-wrapped && cat $(which carve-wrapped) && carve-wrapped ; time carve-wrapped

0.100

src/babashka/bbin/scripts.clj

@@ -194,27 +194,12 @@
 ;
 ; :bbin/end
 
-(require '[babashka.process :as process]
-         '[babashka.fs :as fs]
-         '[clojure.string :as str])
+(require '[babashka.deps :refer [add-deps]])
 
-(def script-root {{script/root|pr-str}})
-(def script-lib '{{script/lib}})
-(def script-coords {{script/coords|str}})
-(def script-main-opts-first {{script/main-opts.0|pr-str}})
-(def script-main-opts-second {{script/main-opts.1|pr-str}})
+(add-deps '{{script/deps}})
 
-(def tmp-edn
-  (doto (fs/file (fs/temp-dir) (str (gensym \"bbin\")))
-    (spit (str \"{:deps {\" script-lib script-coords \"}}\"))
-    (fs/delete-on-exit)))
-
-(def base-command
-  [\"bb\" \"--deps-root\" script-root \"--config\" (str tmp-edn)
-        script-main-opts-first script-main-opts-second
-        \"--\"])
-
-(process/exec (into base-command *command-line-args*))
+(require '[{{script/main-ns}}])
+(apply {{script/main-ns}}/-main *command-line-args*)
 "))
 
 (defn- http-url->script-name [http-url]
@@ -434,7 +419,9 @@
         _ (when (and (not tool-mode) (not (seq main-opts)))
             (throw (ex-info "Main opts not found. Use --main-opts or :bbin/bin to provide main opts."
                             {})))
-        template-opts {:script/meta (->> script-edn-out
+        template-opts {:script/deps (pr-str {:deps script-deps})
+
+                       :script/meta (->> script-edn-out
                                          str/split-lines
                                          (map #(str comment-char " " %))
                                          (str/join "\n"))
@@ -443,12 +430,17 @@
                        :script/coords (binding [*print-namespace-maps* false] (pr-str (val (first script-deps))))}
         template-opts' (if tool-mode
                          (assoc template-opts :script/ns-default (:ns-default script-config))
-                         (assoc template-opts :script/main-opts
-                                              [(first main-opts)
-                                               (if (= "-f" (first main-opts))
-                                                 (fs/canonicalize (fs/file script-root (second main-opts))
-                                                                  {:nofollow-links true})
-                                                 (second main-opts))]))
+                         (let [main-fn (symbol (second main-opts))
+                               main-ns (namespace main-fn)]
+                           (-> template-opts
+                               (assoc :script/main-ns main-ns)
+                               (assoc :script/main-fn main-fn)
+                               (assoc :script/main-opts
+                                      [(first main-opts)
+                                       (if (= "-f" (first main-opts))
+                                         (fs/canonicalize (fs/file script-root (second main-opts))
+                                                          {:nofollow-links true})
+                                         (second main-opts))]))))
         template-str (if tool-mode
                        (if (#{::no-lib} lib)
                          local-dir-tool-template-str