Shut up warning about missing fonts.dtd

pkgs/development/libraries/fontconfig/make-fonts-conf.nix

···
-{runCommand, libxslt, fontconfig, fontDirectories}:
+{ runCommand, libxslt, fontconfig, fontDirectories }:
 
 runCommand "fonts.conf"
-  { 
-    buildInputs = [libxslt];
+  {
+    buildInputs = [ libxslt fontconfig ];
     inherit fontDirectories;
   }
   ''
     xsltproc --stringparam fontDirectories "$fontDirectories" \
       --stringparam fontconfig "${fontconfig}" \
+      --path ${fontconfig}/share/xml/fontconfig \
       ${./make-fonts-conf.xsl} ${fontconfig}/etc/fonts/fonts.conf \
       > $out
   ''