Restore -bs-jsx-mode

Author: nojaf

compiler/bsc/rescript_compiler_main.ml

@@ -256,6 +256,7 @@ let buckle_script_flags : (string * Bsc_args.spec * string) array =
           Js_config.jsx_module := Js_config.jsx_module_of_string i;
           if is_generic then Js_config.jsx_version := Some Jsx_v4),
       "*internal* Set jsx module" );
+    ("-bs-jsx-mode", string_call ignore, "*internal* Set jsx mode, this is no longer used and is a no-op.");
     ( "-bs-package-output",
       string_call Js_packages_state.update_npm_package_path,
       "*internal* Set npm-output-path: [opt_module]:path, for example: \