[wp] add an option to pass extra configuration files to build Why3 config

src/plugins/wp/Why3Provers.ml

@@ -26,7 +26,8 @@
 
 let cfg = lazy
   begin
-    try Why3.Whyconf.init_config None
+    let extra_config = Wp_parameters.Why3ExtraConfig.get () in
+    try Why3.Whyconf.init_config ~extra_config None
     with exn ->
       Wp_parameters.abort "%a" Why3.Exn_printer.exn_printer exn
   end

src/plugins/wp/wp_parameters.ml

@@ -983,6 +983,16 @@ module Why3Flags =
       let help = "Additional options for Why3"
     end)
 
+let () = Parameter_customize.set_group wp_prover_options
+let () = Parameter_customize.no_category ()
+module Why3ExtraConfig =
+  String_list
+    (struct
+      let option_name = "-wp-why3-extra-config"
+      let arg_name = "file,..."
+      let help = "Additional config files for Why3"
+    end)
+
 (* ------------------------------------------------------------------------ *)
 (* --- PO Management                                                    --- *)
 (* ------------------------------------------------------------------------ *)

src/plugins/wp/wp_parameters.mli

@@ -136,6 +136,7 @@ module Steps: Parameter_sig.Int
 module Procs: Parameter_sig.Int
 module ProofTrace: Parameter_sig.Bool
 module Why3Flags: Parameter_sig.String_list
+module Why3ExtraConfig: Parameter_sig.String_list
 
 module Auto: Parameter_sig.String_list
 module AutoDepth: Parameter_sig.Int