download: Allow use of substitutes.

See <https://bugs.gnu.org/18747> for the original report.

* guix/download.scm (url-fetch): Comment out #:local-build? argument.
* guix/git-download.scm (git-fetch): Likewise.
* guix/svn-download.scm (svn-fetch): Likewise.

guix/download.scm

@@ -258,7 +258,11 @@ (define builder
                             #:guile-for-build guile-for-build
 
                             ;; In general, offloading downloads is not a good idea.
-                            #:local-build? #t)
+                            ;;#:local-build? #t
+                            ;; FIXME: The above would also disable use of
+                            ;; substitutes, so comment it out; see
+                            ;; <https://bugs.gnu.org/18747>.
+                            )
           #:guile-for-build guile-for-build
           #:system system))))
 

guix/git-download.scm

@@ -98,7 +98,8 @@ (define build
   (run-with-store store
     (gexp->derivation (or name "git-checkout") build
                       #:system system
-                      #:local-build? #t
+                      ;; FIXME: See <https://bugs.gnu.org/18747>.
+                      ;;#:local-build? #t
                       #:hash-algo hash-algo
                       #:hash hash
                       #:recursive? #t

guix/svn-download.scm

@@ -76,7 +76,8 @@ (define build
   (run-with-store store
     (gexp->derivation (or name "svn-checkout") build
                       #:system system
-                      #:local-build? #t
+                      ;; FIXME: See <https://bugs.gnu.org/18747>.
+                      ;;#:local-build? #t
                       #:hash-algo hash-algo
                       #:hash hash
                       #:recursive? #t