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=71db461a49f27b14bba46e3e6a8f20800c4cef1f'>root</a>/<a href='/guix/log/tests?id=71db461a49f27b14bba46e3e6a8f20800c4cef1f'>tests</a>/<a href='/guix/log/tests/guix-build.sh?id=71db461a49f27b14bba46e3e6a8f20800c4cef1f'>guix-build.sh</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/tests/guix-build.sh?id=71db461a49f27b14bba46e3e6a8f20800c4cef1f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-02-18 14:14:38 +0100'>2022-02-18</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=0ca26437cb36822f9f74ee1a6dbc714477378b13'>guix build: Warn when attempting to build an unsupported package.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-11-08 09:06:14 +0200'>2021-11-08</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=1c94392a13cbdf87e03a644633eb775bf45694a1'>Merge remote-tracking branch 'origin/master' into core-updates-frozen</a></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-11-07 23:10:41 +0100'>2021-11-07</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=4d59596a1c5f6b20870e619cbf67068ac7dd64ff'>ui: 'load*' correctly reports 'read-error' in all cases.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-09-07 14:54:09 +0200'>2021-09-07</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=445eec918332c1b8d4a6ba4baf1322e13076029b'>tests: Adjust '--with-input' test.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-03-23 23:19:57 -0700'>2021-03-23</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=a16eb6c5f97f136b678540ba61f12b2c08e43e13'>Add powerpc64le-linux as a supported Guix architecture.</a><span class='msg-avail'>...</span></td><td>Chris Marusich</td></tr>
<tr><td><span title='2020-10-20 16:30:15 +0200'>2020-10-20</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=8db4ebb0cd9bfdcf1aea63eb8d20eb6af0c87c93'>packages: Better preserve object identity when rewriting.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-10-15 18:50:22 +0200'>2020-10-15</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=5ef1508942ee083ed22b844f5291e59320016b79'>ui: Only suggest modules that export the unbound variable identifier.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a><span class='msg-avail'>...</span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2020-09-27 21:41:08 +0200'>2020-09-27</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=2bf6f962b91123b0474c0f7123cd17efe7f09a66'>packages: 'package-input-rewriting/spec' can rewrite implicit dependencies.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>