Unable to build flatpak

### Pre-flight checklist

- [x] I have read the [contribution documentation](https://github.com/electron/forge/blob/main/CONTRIBUTING.md) for this project.
- [x] I agree to follow the [code of conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project uses.
- [x] I have searched the issue tracker for a bug that matches the one I want to file, without success.

### Forge version

7.8.3

### Electron version

37.4.0

### Operating system

Linux

### Last known working Forge version

_No response_

### Expected behavior

My project has Webpack, React and Tailwind.
Making a flatpak, whether via Github Action or on the host machine causes the same issue:
```
✖ Making a flatpak distributable for linux/x64 [FAILED: flatpak failed with status code 1]
✖ Making distributables [FAILED: flatpak failed with status code 1]

An unhandled rejection has occurred inside Forge:
Error: flatpak failed with status code 1
at ChildProcess. (/home/runner/work/kanban_widget_2/kanban_widget_2/node_modules/@malept/flatpak-bundler/index.js:71:16)
at ChildProcess.emit (node:events:524:28)
at ChildProcess.emit (node:domain:489:12)
at maybeClose (node:internal/child_process:1104:16)
at ChildProcess._handle.onexit (node:internal/child_process:304:5)
```
Any possible causes? Thanks

### Actual behavior

It compiles

### Steps to reproduce

Try to make a flatpak.

### Additional information

_No response_