hurd-boot: Use 'setxattr' instead of invoking settrans.

Note: Using `getxattr' on the Hurd instead of running showtrans does not
work (yet?).

* gnu/build/hurd-boot.scm (setup-translator): Use 'setxattr' instead of
invoking settrans.
* gnu/system.scm (hurd-multiboot-modules): Add --x-xattr-translator-records to
enable xattr-embebbing of translators.

gnu/build/hurd-boot.scm

@@ -140,7 +140,7 @@ set."
             (chmod port mode)))))
     (catch 'system-error
       (lambda _
-        (apply invoke "settrans" "--create" file-name command))
+        (setxattr file-name "gnu.translator" (string-join command "\0" 'suffix)))
       (lambda (key . args)
         (let ((errno (system-error-errno (cons key args))))
           (format (current-error-port) "~a: ~a\n"

gnu/system.scm

@@ -1190,6 +1190,7 @@ a list of <menu-entry>, to populate the \"old entries\" menu."
                 "--device-master-port='${device-port}'"
                 "--exec-server-task='${exec-task}'"
                 "--store-type=typed"
+                "--x-xattr-translator-records"
                 "'${root}'" "'$(task-create)'" "'$(task-resume)'"))
          (target (%current-target-system))
          (libc (if target