Taken from here:
https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/documentation/gtk-doc/respect-xml-catalog-files-var.patch.

--- a/m4/gtkdoc_jh_check_xml_catalog.m4
+++ b/m4/gtkdoc_jh_check_xml_catalog.m4
@@ -5,8 +5,8 @@
 [
 	AC_REQUIRE([JH_PATH_XML_CATALOG],[JH_PATH_XML_CATALOG(,[:])])dnl
 	AC_MSG_CHECKING([for ifelse([$2],,[$1],[$2]) in XML catalog])
-	if $jh_found_xmlcatalog && \
-		AC_RUN_LOG([$XMLCATALOG --noout "$XML_CATALOG_FILE" "$1" >&2]); then
+	# empty argument forces libxml to use XML_CATALOG_FILES variable
+	if AC_RUN_LOG([$XMLCATALOG --noout "" "$1" >&2]); then
 		AC_MSG_RESULT([found])
 		ifelse([$3],,,[$3])
 	else
>
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<div class='path'>path: <a href='/guix/log/?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9'>root</a>/<a href='/guix/log/gnu?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9'>gnu</a>/<a href='/guix/log/gnu/packages?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9'>packages</a>/<a href='/guix/log/gnu/packages/patches?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9'>patches</a>/<a href='/guix/log/gnu/packages/patches/emacs-highlight-stages-add-gexp.patch?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9'>emacs-highlight-stages-add-gexp.patch</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/patches/emacs-highlight-stages-add-gexp.patch?id=820bf78cbc487d28457acc6cb790f4cbd7cc49b9&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
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<tr><td><span title='2022-09-13 00:20:35 -0400'>2022-09-13</span></td><td><a href='/guix/commit/gnu/packages/patches/gdm-wayland-session-wrapper-from-env.patch?id=97313b9b0c5d5977e66f318345523f5a2f3117e5'>gnu: gdm: Update to 42.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/gnome.scm (gdm): Update to 42.0.
[inputs]: Add libgudev.
* gnu/packages/patches/gdm-default-session.patch: Rebase patch.
* gnu/packages/patches/gdm-elogind-support.patch: Likewise.
* gnu/packages/patches/gdm-pass-gdk-pixbuf-loader-env.patch: Likewise.
* gnu/packages/patches/gdm-remove-hardcoded-xwayland-path.patch: Likewise.
* gnu/packages/patches/gdm-wayland-session-wrapper-from-env.patch: Likewise.
</span></span></td><td>Maxim Cournoyer</td></tr>