### Website or app

https://github.com/facebook/react/tree/main/packages/react-devtools-extensions

### Repro steps

Follow the instructions here to build local version of react devtools extension: https://github.com/facebook/react/tree/main/packages/react-devtools-extensions

```
git clone https://github.com/facebook/react.git 
cd react
yarn install
yarn build-for-devtools
```

Stuck on this step everytime `yarn build-for-devtools`:
```
D:\Other\react\node_modules\flow-parser\flow_parser.js:807
throw a}function
^

Error: SignedSource.signFile(...): Cannot sign file without token: <<SignedSource::*O*zOeWoEQle#+L!plEphiEmie@IsG>>
    at Object.<anonymous> (D:\Other\react\node_modules\signedsource\index.js:20:28)
    at Module._compile (node:internal/modules/cjs/loader:1196:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1250:10)
    at Module.load (node:internal/modules/cjs/loader:1074:32)
    at Function.Module._load (node:internal/modules/cjs/loader:909:12)
    at Module.require (node:internal/modules/cjs/loader:1098:19)
    at require (node:internal/modules/cjs/helpers:108:18)
    at Object.<anonymous> (D:\Other\react\scripts\rollup\packaging.js:18:37)
    at Module._compile (node:internal/modules/cjs/loader:1196:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1250:10)
```

Is there anything else I need to set up in order to make this work?

### How often does this bug happen?

Every time

### DevTools package (automated)

_No response_

### DevTools version (automated)

_No response_

### Error message (automated)

_No response_

### Error call stack (automated)

_No response_

### Error component stack (automated)

_No response_

### GitHub query string (automated)

_No response_
let jsonPath = `build/node_modules/${name}/package.json`;
  let packageJSON = JSON.parse(readFileSync(jsonPath));
  let files = packageJSON.files;
  let exportsJSON = packageJSON.exports;
  let browserJSON = packageJSON.browser;
  if (!Array.isArray(files)) {
    throw new Error('expected all package.json files to contain a files field');
  }
  let changed = false;
  for (let i = 0; i < files.length; i++) {
    let filename = files[i];
    let entry =
      filename === 'index.js'
        ? name
        : name + '/' + filename.replace(/\.js$/, '');
    let hasBundle = entryPointsToHasBundle.get(entry);
    if (hasBundle === undefined) {
      
      hasBundle =
        entryPointsToHasBundle.get(entry + '.node') ||
        entryPointsToHasBundle.get(entry + '.browser');