Joystick Input is not working on nightly flatpak build

**Describe the bug**
On the nightly flatpak build, joystick input doesn't seem to be registered.

**To Reproduce**
Steps to reproduce the behavior:
1. Install openscad-nightly using flatpak
2. Open it.
3. Goto Preferences -> Axis and enable Joystick
4. Open a design and try to navigate the view with a joypad attached to the computer

**Expected behavior**
Using a joypad should work.

**Code reproducing the issue**
n/a

**Screenshots**
n/a

**Environment and Version info (please complete the following information):**
- OS: Ubuntu 24.10
- System: Lenovo ThinkPad T14 Gen 1 (AMD) (AMD64 CPU)
- OpenSCAD Version: 2025.03.18 (installed via flatpak)

**Library & Graphics card information**
n/a

**Additional context**
Works with a source-compiled 2025.02.24 build, so I guess it's an issue with flatpak not allowing the application to access the joystick device files.