Build review: FFmpeg build manually

Hello, the latest build is currently was held for a randomly selected review.

While looking at the latest changes, I have noticed you build FFmpeg yourself, even though it is available in the runtime.

Could you clarify why this is done? Why is the build in the runtime not utilized?

Review the package's FFmpeg build configuration and runtime dependencies, then determine why FFmpeg is built manually instead of using the runtime copy. Done means documenting the rationale or agreeing on the intended build approach; the issue names no files or tests to begin with.

Written by the indexing model from the issue text.