fix: rescript-legacy broken for ppx's (#8103)

This resolves PPX errors with "Ill-formed list of warnings" after removal of -bs-v flag. The mtime from being appended to the -bs-v flag, after the change in #7627 it was being appended to the warnings flag instead, causing the compiler error

Fixes #8090

Signed-off-by: Rob <illusionalsagacity@users.noreply.github.com>
Co-authored-by: Christoph Knittel <ck@cca.io>

Author: illusionalsagacity

CHANGELOG.md

@@ -29,6 +29,7 @@
 - Formatter: normalize underscore placeholders in pipe expressions to canonical form (e.g., `a->map2(_, fn)` formats to `a->map2(fn)`). https://github.com/rescript-lang/rescript/pull/8033
 - Fix rewatch panic on duplicate module name. https://github.com/rescript-lang/rescript/pull/8102
 - Fix `let?` unwrap to use actual variable names from pattern instead of hardcoded "x"/"e". When using `let? Some(myVar) = ...`, the variable name `myVar` is now properly propagated in early returns. https://github.com/rescript-lang/rescript/issues/8085
+- Fix 'Ill-formed list of warnings' errors for ppx's with rescript-legacy. https://github.com/rescript-lang/rescript/pull/8103
 
 #### :memo: Documentation
 

compiler/bsb/bsb_ninja_rule.ml

@@ -145,10 +145,6 @@ let make_custom_rules ~(gentype_config : Bsb_config_types.gentype_config)
     (match ppx_files with
     | [] -> ()
     | _ ->
-      Ext_list.iter ppx_files (fun x ->
-          match string_of_float (Unix.stat x.name).st_mtime with
-          | exception _ -> ()
-          | st -> Ext_buffer.add_char_string buf ',' st);
       Ext_buffer.add_char_string buf ' ' (Bsb_build_util.ppx_flags ppx_files));
     (match pp_file with
     | None -> ()