tsup not respecting outDir and target (and probably more) from tsconfig.json

### Current Behavior
When running `tsup`, the build output is generated in the `dist` directory instead of the `lib` directory as specified in my `tsconfig.json`. Similarly, the `target` option in `tsconfig.json` is not being respected.

### Expected Behavior
`tsup` should generate the build output in the `lib` directory and use the `es2022` target as defined in `tsconfig.json`.

### Steps to Reproduce

1. Set up a TypeScript project with the following `tsconfig.json`:

```json
{
"compilerOptions": {
"esModuleInterop": true,
"skipLibCheck": true,
"target": "es2022",
"allowJs": true,
"resolveJsonModule": true,
"moduleDetection": "force",
"isolatedModules": true,
"verbatimModuleSyntax": false,
"module": "ESNext",
"strict": true,
"noImplicitOverride": true,
"moduleResolution": "node",
"sourceMap": true,
"declaration": true,
"incremental": false,
"outDir": "lib",
"baseUrl": ".",
"paths": {
"@/*": [
"./src/*"
]
},
"lib": [
"es2022",
"dom"
]
},
"include": [
"src/**/*.ts"
],
"exclude": [
"node_modules",
"lib",
"coverage"
]
}
```

2. Configure `tsup` with the following `tsup.config.ts`:

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

export default defineConfig({
entry: ['src/**/*.ts'],
dts: true,
shims: true,
clean: true,
skipNodeModulesBundle: true,
format: ['esm'],
tsconfig: './tsconfig.json' // this is rendundant since tsup and tsconfig are in the same dir(?)
})
```

3. Run the build command: `tsup`

### Environment
- `tsup` version: ^7.2.0
- Node.js version: 18

### Additional Context
Despite configuring `tsup` to use the settings from `tsconfig.json`, the build outputs to the `dist` directory, and the target is set to `esnext`.

Reproduce the issue with the provided tsconfig.json and tsup.config.ts, then inspect how tsup loads and applies those configuration options. Done means the build writes to lib instead of dist and uses the es2022 target; verify both outcomes with the supplied project setup.

Written by the indexing model from the issue text.