Add native build and compiler driver

test/test_harness.mli

@@ -0,0 +1,11 @@
+type case = string * (unit -> unit)
+
+val check : string -> bool -> unit
+val fail : string -> string -> unit
+val check_equal_int : string -> int -> int -> unit
+val check_equal_string : string -> string -> string -> unit
+val check_true : string -> string -> bool -> unit
+val expect_diagnostic : string -> (unit -> unit) -> unit
+val run_suite : string -> case list -> unit
+val failure_count : unit -> int
+val case_count : unit -> int