+ Docker as a way of building.

Dockerfile

@@ -0,0 +1,58 @@
+# TOOLCHAIN_PLATFORM is pinned to linux/amd64 so the ARM cross-compilers and
+# qemu-user-static are always x86_64 binaries, matching the tested path.
+# Passing `--platform` through an ARG silences the Docker linter warning about
+# constant --platform values while keeping the behaviour identical.
+ARG TOOLCHAIN_PLATFORM=linux/amd64
+FROM --platform=${TOOLCHAIN_PLATFORM} debian:trixie
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Toolchain and utilities needed by build targets in this repository.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+    bc \
+    bison \
+    build-essential \
+    ca-certificates \
+    cpio \
+    debootstrap \
+    dosfstools \
+    e2fsprogs \
+    fdisk \
+    file \
+    flex \
+    gcc-arm-linux-gnueabi \
+    gcc-arm-linux-gnueabihf \
+    git \
+    kmod \
+    kpartx \
+    libncurses-dev \
+    libssl-dev \
+    libyaml-dev \
+    lzop \
+    make \
+    parted \
+    python3 \
+    python3-pyelftools \
+    python3-venv \
+    qemu-user-static \
+    rsync \
+    sudo \
+    unzip \
+    util-linux \
+    u-boot-tools \
+    wget \
+    xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+
+# brainlilo requires arm-mingw32ce toolchain from cegcc-build releases.
+RUN wget -q -O /tmp/cegcc.zip https://github.com/brain-hackers/cegcc-build/releases/download/2022-04-11-133546/cegcc-2022-04-11-133546.zip \
+    && unzip -q /tmp/cegcc.zip -d /tmp \
+    && mkdir -p /opt \
+    && mv /tmp/cegcc /opt/cegcc \
+    && rm -rf /tmp/cegcc.zip
+
+WORKDIR /work
+
+# Keep entrypoint simple so callers can pass arbitrary make targets.
+CMD ["bash"]