Fix -stop-after lambda (#3128)

Author: ccasin

driver/optcompile.ml

@@ -45,6 +45,7 @@ let compile i typed ~transl_style ~unix ~pipeline =
       |> print_if i.ppf_dump Clflags.dump_lambda Printlambda.program
       |> Compiler_hooks.execute_and_pipe Compiler_hooks.Lambda
       |> (fun program ->
+           if Clflags.(should_stop_after Compiler_pass.Lambda) then () else
            Asmgen.compile_implementation
              unix
              ~pipeline

ocaml/testsuite/tests/tool-ocamlopt-stop-after/stop_after_lambda_warn_error.compilers.reference

@@ -0,0 +1,4 @@
+File "stop_after_lambda_warn_error.ml", line 12, characters 5-12:
+12 | let[@inlined] f x = x
+          ^^^^^^^
+Error (warning 53 [misplaced-attribute]): the "inlined" attribute cannot appear in this context

ocaml/testsuite/tests/tool-ocamlopt-stop-after/stop_after_lambda_warn_error.ml

@@ -0,0 +1,12 @@
+(* TEST
+ setup-ocamlopt.byte-build-env;
+ flags = "-stop-after lambda -warn-error +53";
+ ocamlopt_byte_exit_status = "2";
+ ocamlopt.byte;
+ check-ocamlopt.byte-output;
+*)
+
+(* This should have exit code 2, because we've set -warn-error for a warning
+   that is issued. *)
+
+let[@inlined] f x = x