Ensure next.config.js function is handled for turbo (#43015)

Fixes: #43001

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the
feature request has been accepted for implementation before opening a
PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

packages/next/cli/next-dev.ts

@@ -183,6 +183,12 @@ const nextDev: cliCommand = async (argv) => {
         await loadConfig(PHASE_DEVELOPMENT_SERVER, dir, undefined, true)
       ) as NextConfig
 
+      if (typeof rawNextConfig === 'function') {
+        rawNextConfig = (rawNextConfig as any)(PHASE_DEVELOPMENT_SERVER, {
+          defaultConfig,
+        })
+      }
+
       const checkUnsupportedCustomConfig = (
         configKey = '',
         parentUserConfig: any,