CI: update Debian unstable with libvpl
It should build the QSV/MFX/VPL plugin by default. The image also contains unzip and other updates to the unstable Debian.
The image also has:
- GCC 15.2.0
- a Rust stable toolchain in addition of the nightly one.
- FFmpeg 8
- libpostproc is gone (not built with FFmpeg 8)
- Qt 6.9.2 (from 6.7.2)
Draft on top of !8352 (merged)
Edited by Steve Lhomme