Windows: distFiles contain backslashes since glob v10, producing broken S3 keys downstream

### Summary

`ember-cli-deploy-build@3.0.0` builds `context.distFiles` with:

```js
distFiles: glob.sync('**/*', { cwd: outputPath, nodir: true, dot: true })
```

and depends on `glob@^10.2.6`. Since the glob v9 rewrite, `glob.sync` returns **platform-native path separators** (this was a breaking change from v7/v8, which always returned `/`). On Windows, `distFiles` therefore come out as `assets\app-.js` instead of `assets/app-.js`.

Downstream plugins use these strings verbatim. `ember-cli-deploy-s3` uploads objects under literal-backslash keys (`assets\app.js` — `%5C` in the URL), so every asset ends up unreachable at its expected `assets/...` URL.

### Observed impact

Deploying the same commit:

- from Linux/macOS → works, objects keyed `assets/...`
- from Windows → site is down: `index.html` (uploaded at the bucket root by `ember-cli-deploy-s3-index`, so unaffected) references `assets/...`, CloudFront finds nothing there and the SPA 404-fallback serves `index.html` in place of every script. With `ember-cli-sri` this surfaces as SRI errors where **every asset reports the same computed hash** (the hash of index.html) — quite misleading until you notice the backslash-keyed objects in the bucket.

### Root cause

glob v9+ returns `\`-separated paths on Windows unless the `posix: true` option is passed (see the "Windows" section of the glob README).

### Suggested fix

Pass `posix: true` to both `glob.sync` calls in `index.js` (lines 24 and 58):

```js
glob.sync('**/*', { cwd: outputPath, nodir: true, dot: true, posix: true })
```

This restores the pre-v9 behavior of always emitting `/`, which is what every consumer of `distFiles` expects (S3 keys, manifest entries, URLs).

### Workaround

Pin glob back to v8 for this package, e.g. with yarn resolutions:

```json
"resolutions": { "ember-cli-deploy-build/glob": "^8.1.0" }
```

### Environment

- ember-cli-deploy-build 3.0.0 (glob resolves to 10.5.0)
- ember-cli-deploy 2.0.0, ember-cli-deploy-s3 5.x, ember-cli-deploy-s3-index 4.x
- Windows (any); Linux/macOS unaffected