Add native build and compiler driver

src/diagnostic.mli

@@ -0,0 +1,14 @@
+type t = {
+  file : string;
+  span : Location.span;
+  message : string;
+}
+
+exception Error of t
+
+val set_file : string -> unit
+val file : unit -> string
+val error : Location.span -> ('a, unit, string, 'a) format4 -> 'a
+val make : Location.span -> string -> t
+val to_string : t -> string
+val render : string option -> t -> string