Optimize Dockerfile and use bookworm-slim

Dockerfile

@@ -1,36 +1,51 @@
+# syntax=docker/dockerfile:1.6
 FROM debian:bookworm-slim
 
-# ---------------------------------------------
-# Install required packages
-# ---------------------------------------------
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential cmake ninja-build python3 curl xz-utils ca-certificates \
- && rm -rf /var/lib/apt/lists/*
-
-# ---------------------------------------------
-# Download and install ARM GCC toolchain
-# Supports both Apple Silicon (arm64) and Intel (amd64)
-# ---------------------------------------------
+ARG DEBIAN_FRONTEND=noninteractive
 ARG TARGETARCH
 ARG ARM_GCC_VERSION=13.3.rel1
 
+# Install minimal runtime build deps (keep it small: no build-essential, no git, no python)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates bash cmake ninja-build \
+ && rm -rf /var/lib/apt/lists/*
+
+# Install ARM toolchain depending on container architecture
+# - amd64/arm64: download official Arm tarball (glibc); remove curl/xz afterwards
+# - arm (arm/v7): use Debian packages (no official tarball)
 RUN set -eux; \
-    if [ "${TARGETARCH}" = "arm64" ]; then HOSTARCH="aarch64"; else HOSTARCH="x86_64"; fi; \
-    TARBALL="arm-gnu-toolchain-${ARM_GCC_VERSION}-${HOSTARCH}-arm-none-eabi.tar.xz"; \
-    URL="https://armkeil.blob.core.windows.net/developer/Files/downloads/gnu/${ARM_GCC_VERSION}/binrel/${TARBALL}"; \
-    echo "Downloading ${URL}"; \
-    curl -fL -O "${URL}"; \
-    tar -xf "${TARBALL}"; \
-    rm "${TARBALL}"; \
-    DIR="$(ls -d arm-gnu-toolchain-${ARM_GCC_VERSION}-*-arm-none-eabi)"; \
-    mv "${DIR}" /opt/toolchain
+  case "${TARGETARCH}" in \
+    amd64) \
+      apt-get update && apt-get install -y --no-install-recommends curl xz-utils; \
+      URL="https://developer.arm.com/-/media/Files/downloads/gnu/${ARM_GCC_VERSION}/binrel/arm-gnu-toolchain-${ARM_GCC_VERSION}-x86_64-arm-none-eabi.tar.xz"; \
+      curl -L "$URL" -o /tmp/gcc.tar.xz; \
+      mkdir -p /opt; tar -xJf /tmp/gcc.tar.xz -C /opt; rm -f /tmp/gcc.tar.xz; \
+      ln -s /opt/arm-gnu-toolchain-${ARM_GCC_VERSION}-*/bin/* /usr/local/bin/; \
+      apt-get purge -y curl xz-utils && apt-get autoremove -y; \
+      rm -rf /var/lib/apt/lists/* /usr/share/doc /usr/share/man; \
+      ;; \
+    arm64) \
+      apt-get update && apt-get install -y --no-install-recommends curl xz-utils; \
+      URL="https://developer.arm.com/-/media/Files/downloads/gnu/${ARM_GCC_VERSION}/binrel/arm-gnu-toolchain-${ARM_GCC_VERSION}-aarch64-arm-none-eabi.tar.xz"; \
+      curl -L "$URL" -o /tmp/gcc.tar.xz; \
+      mkdir -p /opt; tar -xJf /tmp/gcc.tar.xz -C /opt; rm -f /tmp/gcc.tar.xz; \
+      ln -s /opt/arm-gnu-toolchain-${ARM_GCC_VERSION}-*/bin/* /usr/local/bin/; \
+      apt-get purge -y curl xz-utils && apt-get autoremove -y; \
+      rm -rf /var/lib/apt/lists/* /usr/share/doc /usr/share/man; \
+      ;; \
+    arm) \
+      apt-get update && apt-get install -y --no-install-recommends \
+        gcc-arm-none-eabi binutils-arm-none-eabi gdb-multiarch \
+      && rm -rf /var/lib/apt/lists/* /usr/share/doc /usr/share/man; \
+      ;; \
+    *) echo "Unsupported TARGETARCH=${TARGETARCH}"; exit 1; \
+  esac
 
-# ---------------------------------------------
-# Add toolchain to PATH
-# ---------------------------------------------
-ENV PATH="/opt/toolchain/bin:${PATH}"
+# Optional: trim docs/examples inside the Arm toolchain to save a few MB
+RUN set -eux; \
+  if ls /opt/arm-gnu-toolchain-* >/dev/null 2>&1; then \
+    find /opt/arm-gnu-toolchain-* -type d \( -name doc -o -name docs -o -name man -o -name info -o -name share \) -prune -exec rm -rf {} + || true; \
+  fi
 
-# ---------------------------------------------
-# Set working directory
-# ---------------------------------------------
 WORKDIR /src
+CMD ["bash"]