build-system/gnu: Adjust to removal of a "bin" output for Libtool.

* guix/build-system/gnu.scm (dist-package): Change libtool:bin input to
  just libtool.

guix/build-system/gnu.scm

@@ -206,7 +206,7 @@ (define* (dist-package p source)
                     (module-ref (resolve-interface module) var))))
          `(("autoconf" ,(ref '(gnu packages autotools) 'autoconf))
            ("automake" ,(ref '(gnu packages autotools) 'automake))
-           ("libtool"  ,(ref '(gnu packages autotools) 'libtool) "bin")
+           ("libtool"  ,(ref '(gnu packages autotools) 'libtool))
            ("gettext"  ,(ref '(gnu packages gettext) 'gnu-gettext))
            ("texinfo"  ,(ref '(gnu packages texinfo) 'texinfo))))))))