gnu: dblatex: Update phase style.

* gnu/packages/docbook.scm (dblatex)[arguments]: Use MODIFY-PHASES
syntax and end phase with #t.

gnu/packages/docbook.scm

@@ -2,6 +2,7 @@
 ;;; Copyright © 2014 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2016 Mathieu Lirzin <mthl@gnu.org>
+;;; Copyright © 2018 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -236,8 +237,8 @@ by no means limited to these applications.)  This package provides XML DTDs.")
        #:use-setuptools? #f
        #:tests? #f                      ;no 'test' command
        #:phases
-       (alist-cons-after
-        'wrap 'set-path
+       (modify-phases %standard-phases
+         (add-after 'wrap 'set-path
            (lambda* (#:key inputs outputs #:allow-other-keys)
              (let ((out (assoc-ref outputs "out")))
                ;; dblatex executes helper programs at runtime.
@@ -247,8 +248,8 @@ by no means limited to these applications.)  This package provides XML DTDs.")
                            (string-append (assoc-ref inputs input)
                                           "/bin"))
                          '("libxslt" "texlive"
-                                    "imagemagick" "inkscape"))))))
-        %standard-phases)))
+                           "imagemagick" "inkscape"))))
+               #t))))))
     (home-page "http://dblatex.sourceforge.net")
     (synopsis "DocBook to LaTeX Publishing")
     (description