download: Disable offloading for downloads.

* guix/download.scm (url-fetch): Use #:local-build? #t.
* guix/git-download.scm (git-fetch): Likewise.

guix/download.scm

@@ -288,12 +288,11 @@ (define builder
                             ;; Honor the user's proxy settings.
                             #:leaked-env-vars '("http_proxy" "https_proxy")
 
-                            ;; In general, offloading downloads is not a good idea.
-                            ;;#:local-build? #t
-                            ;; FIXME: The above would also disable use of
-                            ;; substitutes on old daemons, so comment it out;
-                            ;; see <https://bugs.gnu.org/18747>.
-                            )))))
+                            ;; In general, offloading downloads is not a good
+                            ;; idea.  Daemons before 0.8.3 would also
+                            ;; interpret this as "do not substitute" (see
+                            ;; <https://bugs.gnu.org/18747>.)
+                            #:local-build? #t)))))
 
 (define* (download-to-store store url #:optional (name (basename url))
                             #:key (log (current-error-port)) recursive?)

guix/git-download.scm

@@ -89,9 +89,7 @@ (define build
   (mlet %store-monad ((guile (package->derivation guile system)))
     (gexp->derivation (or name "git-checkout") build
                       #:system system
-                      ;; FIXME: See <https://bugs.gnu.org/18747>.
-                      ;; Uncomment when fixed daemons are widely deployed.
-                      ;;#:local-build? #t
+                      #:local-build? #t           ;don't offload repo cloning
                       #:hash-algo hash-algo
                       #:hash hash
                       #:recursive? #t