[Bug]: can't resolve project's tsconfig path correctly

### Version

```sh
rstest 0.3.2
```

### Details

can't resolve project's tsconfig path correctly.

https://rsbuild.rs/config/source/tsconfig-path

### Reproduce link

https://github.com/web-infra-dev/rslib

### Reproduce Steps

- DEBUG=rstest pnpm test:unit
- search `tsconfig` in  `dist/.rstest-temp/.rsbuild/rspack.config.unit.mjs`