gnu: bash: Use the bootstrap Guile in 'url-fetch/reset-patch-level'.

Fixes <http://bugs.gnu.org/25775>.
Reported by Sirgazil, Ricardo Wurmus, Andy Wingo, and others.

* guix/download.scm (in-band-download): Always use GUILE.  This reverts
9f05908fb1e3707cae593d94688748294717a546.
* gnu/packages/bash.scm (url-fetch/reset-patch-level): Remove #:guile.
Pass %BOOTSTRAP-GUILE as #:guile to 'url-fetch'.  Remove #:guile-for-build
argument in 'gexp->derivation' call.

gnu/packages/bash.scm

@@ -21,6 +21,7 @@
 (define-module (gnu packages bash)
   #:use-module (guix licenses)
   #:use-module (gnu packages)
+  #:use-module (gnu packages bootstrap)
   #:use-module (gnu packages ncurses)
   #:use-module (gnu packages readline)
   #:use-module (gnu packages bison)
@@ -243,14 +244,17 @@ without modification.")
 
 (define* (url-fetch/reset-patch-level url hash-algo hash
                                       #:optional name
-                                      #:key (system (%current-system)) guile)
+                                      #:key (system (%current-system)))
   "Fetch the Bash patch from URL and reset its 'PATCHLEVEL' definition so it
 can apply to a patch-level 0 Bash."
+  ;; Note: Forcefully use %BOOTSTRAP-GUILE here to work around bootstrapping
+  ;; issues when using a daemon that lacks the "download" built-in.  See
+  ;; <https://bugs.gnu.org/25775>.
   (mlet* %store-monad ((name -> (or name (basename url)))
                        (patch (url-fetch url hash-algo hash
                                          (string-append name ".orig")
                                          #:system system
-                                         #:guile guile)))
+                                         #:guile %bootstrap-guile)))
     (gexp->derivation name
                       (with-imported-modules '((guix build utils))
                         #~(begin
@@ -259,7 +263,6 @@ can apply to a patch-level 0 Bash."
                             (substitute* #$output
                               (("PATCHLEVEL [0-6]+")
                                "PATCHLEVEL 0"))))
-                      #:guile-for-build guile
                       #:system system)))
 
 (define bash/fixed                        ;CVE-2017-5932 (RCE with completion)

guix/download.scm

@@ -418,10 +418,7 @@ GnuTLS itself and its dependencies.  See <http://bugs.gnu.org/22774>."
                        ;; hash of the expected result.
                        #:verify-certificate? #f)))))
 
-  (mlet %store-monad ((guile (package->derivation
-                              (or guile
-                                  (@@ (gnu packages bootstrap) %bootstrap-guile))
-                              system)))
+  (mlet %store-monad ((guile (package->derivation guile system)))
     (gexp->derivation file-name builder
                       #:guile-for-build guile
                       #:system system