docs/build.md + docs/zh/build.md rewritten for the Rust workspace:
project-built FFmpeg 8.1 (.cargo/config.toml presets FFMPEG_DIR),
vendored static OCIO on Linux/macOS vs MSYS2 dynamic OCIO on Windows
(with the OCIO_INSTALL_DIR/OCIO_RS_LINK env), the Windows GNU toolchain
requirements (MSYS2 Rust, RUSTFLAGS=-C link-args=-lmsvcrt for the
mingw-w64 _assert forwarding, unset INCLUDE/LIB), Linux audio dev
packages and xvfb headless testing, container packaging, and a
troubleshooting section. The macOS-only guides gain a deprecation
pointer. Also correct two stale comments in tooling/install-deps.sh
(FFmpeg is built by tooling/ffmpeg/build-ffmpeg.sh, not by cargo).
Mike-Solar
498669509a