Search for ASDF configuration files first in user directories, and then in
Guix profiles.

diff -ru a/asdf-3.3.4.lisp b/asdf-3.3.4.lisp
--- a/asdf-3.3.4.lisp	2020-02-14 20:16:22.000000000 +0100
+++ b/asdf-3.3.4.lisp	2020-12-05 11:09:56.066229482 +0100
@@ -12535,10 +12535,15 @@
     (find-preferred-file (system-config-pathnames *output-translations-file*)
                          :direction direction))
   (defun user-output-translations-directory-pathname (&key (direction :input))
-    (xdg-config-pathname *output-translations-directory* direction))
-  (defun system-output-translations-directory-pathname (&key (direction :input))
-    (find-preferred-file (system-config-pathnames *output-translations-directory*)
+    (find-preferred-file (list (xdg-config-home *output-translations-directory*))
                          :direction direction))
+  (defun system-output-translations-directory-pathname (&key (direction :input))
+    `(:output-translations
+      ,@(loop :for dir :in (filter-pathname-set
+                            (xdg-config-dirs
+                             "common-lisp/asdf-output-translations.conf.d/"))
+              :collect `(:include ,dir))
+      :inherit-configuration))
   (defun environment-output-translations ()
     (getenv "ASDF_OUTPUT_TRANSLATIONS"))
 
@@ -12921,10 +12926,15 @@
     (find-preferred-file (system-config-pathnames *source-registry-file*)
                          :direction direction))
   (defun user-source-registry-directory (&key (direction :input))
-    (xdg-config-pathname *source-registry-directory* direction))
-  (defun system-source-registry-directory (&key (direction :input))
-    (find-preferred-file (system-config-pathnames *source-registry-directory*)
+    (find-preferred-file (list (xdg-config-home *source-registry-directory*))
                          :direction direction))
+  (defun system-source-registry-directory (&key (direction :input))
+    `(:source-registry
+      ,@(loop :for dir :in (filter-pathname-set
+                            (xdg-config-dirs
+                             "common-lisp/source-registry.conf.d/"))
+              :collect `(:include ,dir))
+      :inherit-configuration))
   (defun environment-source-registry ()
     (getenv "CL_SOURCE_REGISTRY"))