fix(build): build with 5.4.0

Author: PerfectLaugh

plugins/x86/x86_legacy_bil_pp.ml

@@ -511,13 +511,15 @@ let buf = Buffer.create 57
 
 let ft =
   let out_string = Stdlib.Buffer.add_substring buf
-  and out_spaces _ = Stdlib.Buffer.add_char buf ' ' in
+  and out_spaces _ = Stdlib.Buffer.add_char buf ' '
+  and out_width : string -> pos:int -> len:int -> int = fun s ~pos ~len -> len in
   let ft = Format.formatter_of_buffer buf in
   Format.pp_set_formatter_out_functions ft
     {
       Format.out_string;
       out_flush = ignore;
       out_spaces;
+      out_width;
       out_newline = ignore;
       out_indent = out_spaces;
     };