Fixed: Build broken with latest nv-codec-headers (12.1.xx.x)

[eumagga0x2a]

Currently, FFmpeg libraries in Avidemux core fail to compile when built against the latest NVIDIA Video SDK headers (nv-codec-headers) as shipped e.g. by Fedora. As a workaround, please downgrade to 12.0.xx.x or 11.x.xx.x for now.

[eumagga0x2a]

Build failure fixed, unpinning the topic.