WIP: Add org.freedesktop.Platform.GL{,32}.bumblebee

Description

This MR adds an extension that mounts the primus package in the sandbox when a host Bumblebee daemon is detected by Flatpak. The primusrun script can then be used to offload GLX rendering to the discrete GPU in Optimus laptops. At the moment a few manual additions to flatpak run are required, so this is still work-in-progress.

TODO

• Package primus as a Flatpak extension for org.freedesktop.Platform.GL{,32}. – DONE
• Get primusrun to offload GLX rendering for 64-bit and 32-bit executables. – DONE (see example below)
• Get primusrun to offload GLX rendering for 32-bit executables relying on multilib libraries - DONE
• Add primusrun to PATH for easier execution. – still need to figure out how.
• Add a debug build.
• Add support in Flatpak to detect inactive NVIDIA drivers. – done in side-branch.
• Add support in Flatpak to detect the Bumblebee daemon and expose its socket and X display.
• Figure out why --network and --device=all permissions are required to make this work.
• Bonus: investigate using EGL for rendering to eliminate X11 permission requirements.

Example

Prerequisites

• Optimus laptop with the integrated GPU used as default.
• NVIDIA drivers installed on the host and the same driver version installed in Flatpak.
• Bumblebee daemon running on the host.

Procedure

1. Install the Bumblebee extensions:

   $ flatpak install repo org.freedesktop.Platform.GL{,32}.bumblebee

   NOTE: you'll need to build them locally for now.
2. Run a Flatpak which relies on GLX rendering. I chose org.freedesktop.GlxInfo for this example, but com.valvesoftware.Steam would work as well:

   $ FLATPAK_GL_DRIVERS='nvidia-396-54:bumblebee' flatpak run \
   --command=bash \
   --device=all --share=network --filesystem=/run/bumblebee.socket --filesystem=/tmp/.X11-unix \
   org.freedesktop.GlxInfo

   NOTE: make sure to replace "nvidia-396-54" with your NVIDIA driver version. You can use modinfo nvidia -F version to find the correct version, but make sure to replace . with - in the version string.
3. You can now offload GLX rendering using primusrun inside the sandbox:

   bash-4.4$ /usr/lib/x86_64-linux-gnu/GL/bumblebee/bin/primusrun -- glxgears -info | grep RENDERER
   GL_RENDERER   = GeForce GT 750M/PCIe/SSE2

   NOTE: if you used com.valvesoftware.Steam, edit a game's launch options as described in this support page. Make sure to specify the full path to primusrun as shown above.

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CC: @valentindavid