PNG in Custom Logo causes silent build failure.

Follow the custom logo flow and add a png
```
/** @jsxRuntime classic */
/** @jsx jsx */
import Link from 'next/link';
import { jsx, H3 } from '@keystone-ui/core';
import Logo from './Logo.png';

export const CustomLogo = () => {
return (

LegendBoulder After

);
};
```
Run `yarn build`

The build should complete successfully, it instead hangs indefinitely.
This flow works fine in `yarn dev`

Replicated both within the keystone repo and in an external reproduction.
Replicated in node 14.17, but appears to be the case in multiple node versions.
Likely a next build issue, that isn't being surfaced.

Original report here: https://keystonejs.slack.com/archives/C01STDMEW3S/p1639128427068300

Start by reproducing the custom logo flow with the PNG import shown in the issue and run `yarn build`, comparing it with `yarn dev`. Trace the Next.js build path for the custom logo and determine why the build hangs without reporting an error; done means the reproduction builds successfully and the failure is surfaced or resolved.

Written by the indexing model from the issue text.