This combined package preserves exact toolchain identity per component.

FFmpeg uses the GCC/MinGW 12 toolchain identified by
toolchain/ffmpeg-gcc12/TOOLCHAIN-MANIFEST.json and its accompanying
copyright notices. FFprobe uses the separately identified GCC 15.2.0
cross-toolchain recorded in toolchain/ffprobe-gcc15/ and its build
recipe. FFprobe does not redistribute a GCC/MinGW runtime DLL.
