rebirth: Properly terminate generated proc in ES output

* build-aux/bootstrap/rebirth/es.scm (cdfn-proc): Add missing semicolon.
  This was causing serious problems when the folloiwng line introduced
  lexical scope, since that encloses the scope in a self-executing function,
  but the opening parenthesis were interpreted as invoking the code
  preceding it.

build-aux/bootstrap/rebirth.scm

@@ -492,7 +492,7 @@
                "\n})(Object.create(_env));}"
                (if named?
                    (string-append ";_env." id " = " id
-                                  ";_env.root." id " = " id)
+                                  ";_env.root." id " = " id ";")
                    ""))))
       ;; Immediately evaluate to make available to macros during
       ;; compilation.  See procedure notes above.