run: Unset EGL driver paths

[fooishbar]

Similar to how b8d8d80 inhibited passthrough of environment variables pointing the Vulkan loader towards a specific ICD, do the same for the EGL paths used by libglvnd to discover the GL driver to use.

These paths are typically referencing the host filesystem; if the user is referencing paths only available in the sandbox, they can use --env or overrides for them.

---

cf. #5553, cc @TingPing

It's worth noting that this doesn't apply to GLX because it only takes a vendor name, then loads a DSO based on that name from the dlopen path.

[smcv]

For completeness, should we also be doing this for __EGL_EXTERNAL_PLATFORM_CONFIG_FILENAMES and __EGL_EXTERNAL_PLATFORM_CONFIG_DIRS?

[smcv]

...and perhaps also VK_LAYER_PATH, VK_ADD_LAYER_PATH, VK_ADD_DRIVER_FILES?

[fooishbar]

Yeah nice, thanks. To be honest I hadn't looked too closely at the Vulkan loader for this one, and I'd also completely forgotten that NVIDIA EGLStreams shim even existed.

[smcv]

CI failure looks like Github/Microsoft brokenness rather than your fault:

E: Failed to fetch https://packages.microsoft.com/ubuntu/22.04/prod/dists/jammy/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)

[smcv]

CI failure looks like Github/Microsoft brokenness rather than your fault

I'm attempting to fix this in #5786.

[smcv]

ensure_driver_environment() in https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/blob/main/steam-runtime-tools/system-info.c?ref_type=heads has a long list of similar search-path/driver-choice environment variables, although as you noted above, some of them (like the __GLX_VENDOR_LIBRARY_NAME) are just a basename or similar and not a complete absolute path or list of paths.

[fooishbar]

thanks for all your help, and @rmader for rubber-ducking me to get here in the first place :)

[rmader]

Thanks for fixing this, I guess it will avoid a lot of cursing :P