build: Disable grafting in sanity checks.

* build-aux/check-available-binaries.scm: Wrap body in 'parameterize'
  form that clears '%graft?'.
* build-aux/check-final-inputs-self-contained.scm: Likewise.

build-aux/check-available-binaries.scm

@@ -29,6 +29,7 @@
              (srfi srfi-26))
 
 (with-store store
+  (parameterize ((%graft? #f))
     (let* ((native (append-map (lambda (system)
                                  (map (cut package-derivation store <> system)
                                       (list %bootstrap-tarballs emacs)))
@@ -52,4 +53,4 @@
         (when result
           (format (current-error-port) "~a packages found substitutable~%"
                   (length total)))
-      (exit result))))
+        (exit result)))))

build-aux/check-final-inputs-self-contained.scm

@@ -73,8 +73,9 @@ refer to the bootstrap tools."
 
 ;; Entry point.
 (with-store store
+  (parameterize ((%graft? #f))
     (set-build-options store #:use-substitutes? #t)
 
     (for-each (cut test-final-inputs store <>)
-            %supported-systems))
+              %supported-systems)))