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
a269b0549ef5ce10823a'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a'>root</a>/<a href='/guix/log/etc?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a'>etc</a>/<a href='/guix/log/etc/snippets?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a'>snippets</a>/<a href='/guix/log/etc/snippets/yas?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a'>yas</a>/<a href='/guix/log/etc/snippets/yas/scheme-mode?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a'>scheme-mode</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/etc/snippets/yas/scheme-mode?id=b25d2ad5c7bba8c2818ea269b0549ef5ce10823a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-10-21 00:27:25 +0200'>2023-10-21</span></td><td><a href='/guix/commit/etc/snippets/yas/scheme-mode?id=e011961f99e3cab8ff1972de2b4659e972bb00a0'>build-system: Add zig-build-system.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/build-system/zig.scm: New file.
* guix/build/zig-build-system.scm: New file.
* Makefile.am: Add them.
* doc/guix.texi: Document it.
* etc/snippets/yas/scheme-mode/guix-package (build-system): Add
  zig-build-system.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Ekaitz Zarraga</td></tr>
<tr><td><span title='2023-02-19 21:13:23 -0500'>2023-02-19</span></td><td><a href='/guix/commit/etc/snippets/yas/scheme-mode?id=633ead4afc78cfe65d9c8e629a4af4a80d969eb4'>etc: Add a news entry snippet.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/snippets/yas/scheme-mode/guix-news-entry: New file.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-08-30 11:50:15 +0200'>2022-08-30</span></td><td><a href='/guix/commit/etc/snippets/yas/scheme-mode?id=47c11772dfe840a536ed7ec438fe832878f51054'>etc: Update yasnippet build system list.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/snippets/yas/scheme-mode/guix-package (build-system): Add
chicken-build-system, minetest-build-system, rebar-build-system
and renpy-build-system.

Signed-off-by: Liliana Marie Prikler &lt;liliana.prikler@gmail.com&gt;
</span></span></td><td>Nicolas Graves</td></tr>
<tr><td><span title='2022-08-30 11:50:14 +0200'>2022-08-30</span></td><td><a href='/guix/commit/etc/snippets/yas/scheme-mode?id=c4acaf412064568a546034871a9e0d3888aa7937'>etc: Add tempel snippets.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/snippets/tempel/scheme-mode: New file.
* etc/snippets/tempel/text-mode: New file.
* etc/snippets/scheme-mode: Moved from here...
* etc/snippets/yas/scheme-mode: ... to here.
* etc/snippets/text-mode: Moved from here...
* etc/snippets/yas/text-mode: ... to here.
* doc/contributing.texi ("The Perfect Setup"): Adjust yasnippet setup
accordingly.  Add tempel setup.

Signed-off-by: Liliana Marie Prikler &lt;liliana.prikler@gmail.com&gt;
</span></span></td><td>Nicolas Graves</td></tr>