(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>