drm 2.4.101

See merge request !2412

Update Mesa to 20.0.4

See merge request !2410

Swap usercustomize and sitecustomize

Closes #997

See merge request !2400

Update Mesa to 20.0.3

See merge request !2407

elements/components/sdl2.bst: Update to 2.0.12

Closes #995

See merge request !2404

.gitlab-ci.yml: allow interrupting track and build jobs

See merge request !2402

This allows cancelling redundant pipelines that have already started

See https://docs.gitlab.com/ce/ci/yaml/#interruptible

Update Vulkan to 1.2.131

See merge request !2385

llvm: Update to 10.0.0

See merge request !2391

components/linux.bst: add more virtio options and uinput

See merge request !2395

uinput and vsockets are needed by spice-vdagent, and the rest seems
useful in a VM.

Update Mesa to 20.0.2

See merge request !2393

Update builder image to latest

See merge request !2382

fix bug in create_mirrors_from_problem_list.py

See merge request !2379

Add more detail to README-Create-mirrors-script.md, and slightly
improve some help messages in create_mirrors_from_problem_list.py.

Remove 'mirror_problem_list.json' from the artefacts of the nightly
schedule job. This avoids confusion with 'unmirrored_sources_list.json
(and therefore makes the user-experience clearer/cleaner for this job).

create_mirrors_from_problem_list.py was not completing the final 'git
push' instruction, except in automatic mode.

Delete stale openh264 files

See merge request !2387

New repo is here:
https://gitlab.com/freedesktop-sdk/openh264-extension

needed by GNOME's evolution-data-server

also drop libcroco as it is no longer needed

pulseaudio: Enable bluetooth

See merge request !2376

Update gcc dependencies

See merge request !2372

Add xdg portals to desktop VM

See merge request !2358