Currently, Windows some dependencies are built with MinGW/GCC 3.x
this commit removes that, in favor of building them with MSVC
via msys2. This will make it easier in the future to offer Win/Arm64
builds of blender.
Notable changes:
- This change drops support for the external libxvid library in favor
of ffmpegs built in support for this format. This has been done with
permission from the VFX module.
Pull Request: blender/blender#105502