[FEAT]: activate OpenCL for the flatpak application

[claudioandre-br]

Description

Currently, OpenCL flatpak works (could work [1]) for the CPU [2].

At the moment, the only way to use a john "containerized package" with GPU access is via Docker. Offering access to all important john resources securely via flapak [3] is something that offers value to the end user.

It seems this is/will be possible soon (at least for NVIDIA):
https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/issues/1535

[1] OpenCL is disabled in flatpak binaries.
[2] I've tested it a bit, but unfortunately I don't own any suitable hardware. I've never tested it with a GPU.
[3] I mean, OpenCL in a sandboxed app.

Alternatives Considered

No response

Additional Context

Deploy john with OpenCL support in a secure, sandboxed and containerized way will allow users to use the full power of the tool, protected against a good number of flaws that may exist in the binary during the development process.

• I won't be able to test it (no hardware). But the changes are safe and easy to “understand”: enable OpenCL and add the necessary permissions/extensions.
• I use snap, but IMO flatpak is taking a better route.

[claudioandre-br]

See flathub/com.openwall.John#13