using `clean: true` with multiple builds leads to missing output files

```ts
import { defineConfig } from 'tsup'

export default defineConfig([
{
entry: ['src/index.ts'],
format: ['cjs', 'esm'],
clean: true,
},
{
entry: ['src/index.ssr.ts'],
format: ['esm'],
clean: true,
},
])
```

When I save either entry point, the output file for the other build is erroneously deleted.

I tried enabling `clean: true` for the first build only, but it didn't help.