gnu: Use 'search-input-directory' for glibc locale data.

* gnu/packages/gnome.scm (gnome-desktop)[arguments]: Use
'search-input-directory' when searching for glibc's "lib/locale".
* gnu/packages/gnome.scm (geocode-glib): Likewise.
* gnu/packages/package-management.scm (flatpak): Likewise.

gnu/packages/gnome.scm

@@ -2187,9 +2187,8 @@ offline sources, providing a centralized place for managing your contacts.")
              (system "Xvfb :1 &")
              (setenv "DISPLAY" ":1")
              (setenv "GUIX_LOCPATH"
-                     (string-append (assoc-ref inputs "glibc-locales")
-                                    "/lib/locale"))
-             #t)))))
+                     (search-input-directory inputs
+                                             "lib/locale")))))))
     (native-inputs
      `(("glib:bin" ,glib "bin") ; for gdbus-codegen
        ("glibc-locales" ,glibc-locales) ; for tests
@@ -5321,9 +5320,7 @@ permission from user.")
          (add-before 'check 'set-locales
            (lambda* (#:key inputs #:allow-other-keys)
              (setenv "GUIX_LOCPATH"
-                     (string-append (assoc-ref inputs "glibc-locales")
-                                    "/lib/locale"))
-             #t)))))
+                     (search-input-directory inputs "lib/locale")))))))
     (native-inputs
      `(("glib:bin" ,glib "bin") ; for glib-mkenums
        ("glibc-locales" ,glibc-locales) ; for tests

gnu/packages/package-management.scm

@@ -1386,8 +1386,8 @@ the boot loader configuration.")
         (add-after 'unpack 'fix-tests
           (lambda* (#:key inputs #:allow-other-keys)
             (copy-recursively
-             (string-append (assoc-ref inputs "glibc-utf8-locales")
-                            "/lib/locale/") "/tmp/locale")
+             (search-input-directory inputs "lib/locale")
+             "/tmp/locale")
             (for-each make-file-writable (find-files "/tmp"))
             (substitute* "tests/make-test-runtime.sh"
               (("cp `which.*") "echo guix\n")