Lint docker file

Signed-off-by: luke <luke.parkin@arm.com>

Author: Luke-Parkin

Dockerfile

@@ -1,26 +1,27 @@
 FROM zephyrprojectrtos/ci-base:v0.28.5 AS build
-# 1. Install minimal Zephyr SDK for Arm
 ARG SDK_VERSION=0.17.4
-RUN wget -q https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v${SDK_VERSION}/zephyr-sdk-${SDK_VERSION}_linux-${HOSTTYPE}_minimal.tar.xz && \
-    tar -xf zephyr-sdk-${SDK_VERSION}_linux-${HOSTTYPE}_minimal.tar.xz && \
-    rm zephyr-sdk-${SDK_VERSION}_linux-${HOSTTYPE}_minimal.tar.xz && \
-    cd zephyr-sdk-${SDK_VERSION} && \
-    ./setup.sh -t arm-zephyr-eabi -h -c
+
+RUN set -eu; \
+    ARCH="$(uname -m)"; \
+    mkdir -p /opt; \
+    wget -q "https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v${SDK_VERSION}/zephyr-sdk-${SDK_VERSION}_linux-${ARCH}_minimal.tar.xz" && \
+    tar -C /opt -xf "zephyr-sdk-${SDK_VERSION}_linux-${ARCH}_minimal.tar.xz" && \
+    rm -f "zephyr-sdk-${SDK_VERSION}_linux-${ARCH}_minimal.tar.xz"
+
+WORKDIR /opt/zephyr-sdk-${SDK_VERSION}
+RUN ./setup.sh -t arm-zephyr-eabi -h -c
+
 # 2. West init
 WORKDIR /workspace
-ADD west.yml .
-RUN west init -l .
-RUN west update --narrow --fetch-opt=--depth=1
-ADD . .
+COPY west.yml .
+RUN west init -l . && \
+    west update --narrow --fetch-opt=--depth=1
+COPY . .
 # 3. Build
-# List of boards supported by Zephyr: https://docs.zephyrproject.org/latest/boards/index.html
-# Example usage:
-# --build-arg BOARD=imx93_evk/mimx9352/m33
-# --build-arg BOARD=stm32mp257f_dk/stm32mp257fxx/m33
 ARG BOARD
-RUN test -n "$BOARD" || (echo "BOARD not set" && false)
-RUN west build -p -b $BOARD
+RUN test -n "$BOARD" || (echo "BOARD not set" && false) && \
+    west build -p -b "$BOARD"
 
 FROM scratch
 COPY --from=build /workspace/build/zephyr/zephyr.elf /zephyr.elf
-ENTRYPOINT [ "zephyr.elf" ]
+ENTRYPOINT ["/zephyr.elf"]