system: hurd: Remove custom <manifest> gexp compiler.

This is superseded by <profile>, which was added in
ef674a24c5.

* gnu/system/hurd.scm (compile-manifest): Remove.
(cross-hurd-image)[system-profile]: Define using 'profile'.

gnu/system/hurd.scm

@@ -41,16 +41,6 @@
 ;;;
 ;;; Code:
 
-;; XXX: Surely this belongs in (guix profiles), but perhaps we need high-level
-;; <profile> objects so one can specify hooks, etc.?
-(define-gexp-compiler (compile-manifest (manifest
-                                         (@@ (guix profiles) <manifest>))
-                                        system target)
-  "Lower MANIFEST as a profile."
-  (profile-derivation manifest
-                      #:system system
-                      #:target target))
-
 (define %base-packages/hurd
   (list hurd bash coreutils file findutils grep sed
         guile-3.0 guile-colorized guile-readline
@@ -71,8 +61,10 @@
                          (manifest-entry-dependencies entry)))))
 
   (define system-profile
-    (map-manifest-entries cross-built-entry
+    (profile
-                          (packages->manifest %base-packages/hurd)))
+     (content
+      (map-manifest-entries cross-built-entry
+                            (packages->manifest %base-packages/hurd)))))
 
   (define grub.cfg
     (let ((hurd (cross-built hurd))