build-system/gnu: Delay resolution of (@ (gnu packages cmake) cmake).

* guix/build-system/cmake.scm (default-cmake): New procedure.
  (cmake-build): Use it.

guix/build-system/cmake.scm

@@ -35,13 +35,20 @@
 ;;
 ;; Code:
 
+(define (default-cmake)
+  "Return the default CMake package."
+
+  ;; Do not use `@' to avoid introducing circular dependencies.
+  (let ((module (resolve-interface '(gnu packages cmake))))
+    (module-ref module cmake)))
+
 (define* (cmake-build store name source inputs
                      #:key (guile #f)
                      (outputs '("out")) (configure-flags ''())
                      (search-paths '())
                      (make-flags ''())
                      (patches ''()) (patch-flags ''("--batch" "-p1"))
-                     (cmake (@ (gnu packages cmake) cmake))
+                     (cmake (default-cmake))
                      (out-of-source? #f)
                      (tests? #t)
                      (test-target "test")