Structure 'echo' like all the other built-ins.

* gash/built-ins/echo.scm (echo): Rename this...
(main): ...to this, and do not export it.
* gash/built-ins.scm: Reference the 'main' function of the 'echo'
module using '@@'.

gash/built-ins.scm

@@ -17,7 +17,6 @@
 ;;; along with Gash.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gash built-ins)
-  #:use-module (gash built-ins echo)
   #:export (search-built-ins
             search-special-built-ins))
 
@@ -72,7 +71,7 @@
     ("unalias" . ,undefined)
     ("wait" . ,undefined)
     ;; Other built-ins.
-    ("echo" . ,echo)))
+    ("echo" . ,(@@ (gash built-ins echo) main))))
 
 (define (search-special-built-ins name)
   (assoc-ref *special-built-ins* name))

gash/built-ins/echo.scm

@@ -20,8 +20,7 @@
 (define-module (gash built-ins echo)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
-  #:use-module (srfi srfi-26)
-  #:export (echo))
+  #:use-module (srfi srfi-26))
 
 ;;; Commentary:
 ;;;
@@ -57,7 +56,7 @@
        (char=? (string-ref str 0) #\-)
        (string-every (cut member <> '(#\E #\e #\n)) (substring str 1))))
 
-(define (echo . args)
+(define (main . args)
   (let* ((options (append-map (compose cdr string->list)
                               (take-while option? args)))
          (args (drop-while option? args))