src: improve error message for invalid child stdio type in spawn_sync

PR-URL: https://github.com/nodejs/node/pull/57589
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

src/spawn_sync.cc

@@ -1055,7 +1055,10 @@ Maybe<int> SyncProcessRunner::ParseStdioOption(int child_fd,
     return Just(AddStdioInheritFD(child_fd, inherit_fd));
   }
 
-  UNREACHABLE("invalid child stdio type");
+  Utf8Value stdio_type(env()->isolate(), js_type);
+  fprintf(stderr, "invalid child stdio type: %s\n", stdio_type.out());
+
+  UNREACHABLE();
 }
 
 int SyncProcessRunner::AddStdioIgnore(uint32_t child_fd) {