gnu: docbook-xml: Use XSLT to patch catalog.xml.

(sxml transforms) are unsuited here due to guile-bug #20339.

* gnu/packages/aux-files/xml/patch-catalog-xml.xsl: New file.
* Makefile.am: Register it.
* gnu/packages/docbook.scm (docbook-xml-5)[native-inputs]: Add libxslt.
[arguments]: Add phase to patch catalog.xml using XSLT.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>

Makefile.am

@@ -436,7 +436,8 @@ AUX_FILES =						\
   gnu/packages/aux-files/python/sanity-check.py		\
   gnu/packages/aux-files/python/sitecustomize.py	\
   gnu/packages/aux-files/renpy/renpy.in	\
-  gnu/packages/aux-files/run-in-namespace.c
+  gnu/packages/aux-files/run-in-namespace.c		\
+  gnu/packages/aux-files/xml/patch-catalog-xml.xsl
 
 # Templates, examples.
 EXAMPLES =					\

gnu/packages/aux-files/xml/patch-catalog-xml.xsl

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+SPDX-FileCopyrightText: 2023 Bruno Victal <mirai@makinata.eu>
+SPDX-License-Identifier: ISC
+
+Fix uri attributes to point to paths in the store.
+-->
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
+  <xsl:output method="xml"/>
+  <xsl:param name="prefix">/</xsl:param>
+  <!-- begin identity transform -->
+  <xsl:template match="@*|node()">
+    <xsl:copy>
+      <xsl:apply-templates select="@*|node()"/>
+    </xsl:copy>
+  </xsl:template>
+  <!-- end identity transform -->
+
+  <xsl:template match="@uri">
+    <xsl:attribute name="uri">
+      <xsl:value-of select="concat('file://', $prefix, '/', .)"/>
+    </xsl:attribute>
+  </xsl:template>
+</xsl:stylesheet>

gnu/packages/docbook.scm

@@ -8,6 +8,7 @@
 ;;; Copyright © 2021 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2021 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2021 Andrew Whatson <whatson@gmail.com>
+;;; Copyright © 2023 Bruno Victal <mirai@makinata.eu>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -71,11 +72,22 @@
             (lambda _
               ;; XXX: These files do not need 0755 permission.
               (for-each (cut chmod <> #o644) (find-files "."))))
+          (add-before 'install 'patch-catalog-xml
+            (lambda* (#:key inputs #:allow-other-keys)
+              (let ((xsltproc (search-input-file inputs "/bin/xsltproc"))
+                    (dtd-path (string-append #$output "/xml/dtd/docbook")))
+                (invoke xsltproc "--nonet" "--noout"
+                        "--stringparam" "prefix" dtd-path
+                        "--output" "catalog.xml.new"
+                        #$(local-file
+                           (search-auxiliary-file "xml/patch-catalog-xml.xsl"))
+                        "catalog.xml")
+                (rename-file "catalog.xml.new" "catalog.xml"))))
           (replace 'install
             (lambda _
               (let ((dtd-path (string-append #$output "/xml/dtd/docbook")))
                 (copy-recursively "." dtd-path)))))))
-    (native-inputs (list unzip))
+    (native-inputs (list libxslt unzip))
     (home-page "https://docbook.org")
     (synopsis "DocBook XML DTDs for document authoring")
     (description