build-system/composer: Do not import host-side Guile-JSON modules.

Importing host-side (json …) modules would make builds dependent on the
Guile-JSON version currently installed by the user.  Use
‘with-extensions’ instead.

* guix/build-system/composer.scm (%composer-build-system-modules):
Remove (json …) modules.
(composer-build)[guile-json]: New variable.
[builder]: Wrap body in ‘with-extensions’.

Change-Id: Ibe565572d60481b31292d73c6fa23d42aa3ceecb

guix/build-system/composer.scm

@@ -62,10 +62,6 @@
   ;; Build-side modules imported by default.
   `((guix build composer-build-system)
     (guix build union)
-    (json)
-    (json builder)
-    (json parser)
-    (json record)
     ,@%gnu-build-system-modules))
 
 (define* (lower name
@@ -124,7 +120,12 @@
                                     (guix build utils))))
   "Build SOURCE using PHP, and with INPUTS. This assumes that SOURCE provides
 a 'composer.json' file as its build system."
+  (define guile-json
+    (module-ref (resolve-interface '(gnu packages guile))
+                'guile-json-4))
+
   (define builder
+    (with-extensions (list guile-json)
       (with-imported-modules imported-modules
         #~(begin
             (use-modules #$@(sexp->gexp modules))
@@ -148,7 +149,7 @@ a 'composer.json' file as its build system."
                    #:patch-shebangs? #$patch-shebangs?
                    #:strip-binaries? #$strip-binaries?
                    #:strip-flags #$strip-flags
-                 #:strip-directories #$strip-directories)))))
+                   #:strip-directories #$strip-directories))))))
 
   (gexp->derivation name builder
                     #:system system