Accept and ignore ppx.driver fields (#588)

CHANGES.md

@@ -10,6 +10,9 @@ next
 - Reduce interleaving in the scheduler in an attempt to make Jbuilder
   keep file descriptors open for less long (#586)
 
+- Accept and ignore `ppx.driver` fields in library stanzas, in
+  preparation for the generic ppx driver system (#588)
+
 1.0+beta18 (25/02/2018)
 -----------------------
 

src/jbuild.ml

@@ -660,6 +660,7 @@ module Library = struct
        field      "self_build_stubs_archive" (option string) ~default:None >>= fun self_build_stubs_archive ->
        field_b    "no_dynlink"                                             >>= fun no_dynlink               ->
        Sub_system_info.record_parser () >>= fun sub_systems ->
+       field "ppx.driver" ignore ~default:() >>= fun () ->
        return
          { name
          ; public