Add support for multi-arch container builds

docker/build.sh

@@ -25,7 +25,28 @@
 && target_build_arch=x86 \
 || target_build_arch="$TARGET_BUILD_ARCH"
 
+case "$target_build_arch" in
+    armv8*)
+        container_platform="linux/arm64"
+        ;;
+
+    arm*) # Unknown "arm" are marked as 32-bit platforms
+        container_platform="linux/arm"
+        ;;
+
+    x86|x86_64) # Ubuntu images don't have a i386 tag, must run the container with a amd64 tag, let's just not support i386 builders
+        container_platform="linux/amd64"
+        ;;
+
+    *)
+        echo "Unsupported container platform: $target_build_arch"
+        exit 1
+        ;;
+esac
+
 docker build \
+    --platform "$container_platform" \
+    --build-arg "TARGET_CONTAINER_BUILD_ARCH=$target_build_arch" \
     -t open.mp/build:ubuntu-${ubuntu_version} \
     build_ubuntu-${ubuntu_version}/ \
 || exit 1
@@ -41,6 +62,7 @@ done
 docker run \
     --rm \
     -t \
+    --platform "$container_platform" \
     -w /code \
     -v $PWD/..:/code \
     -v $PWD/build:/code/build \

docker/build_ubuntu-22.04/Dockerfile

@@ -1,24 +1,48 @@
 FROM ubuntu:22.04
-RUN \
-    dpkg --add-architecture i386 && \
-    apt-get update && \
+ARG TARGET_CONTAINER_BUILD_ARCH
+
+# Fix for some rootless builders
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Base layer
+RUN apt-get update && \
     apt-get install -y \
         cmake \
         ninja-build \
         clang-11 \
-        python3-pip \
-        gcc-9-multilib \
-        g++-9-multilib \
-        libstdc++-11-dev:i386 \
-    && \
+        python3-pip && \
+    rm -rf /var/lib/apt/lists/* && \
     useradd -m user && \
     su user -c 'pip3 install --user conan'
 
+# Arch-specific layer
+RUN case "$TARGET_CONTAINER_BUILD_ARCH" in \
+        x86_64|x86) \
+            dpkg --add-architecture i386 && \
+            apt-get update && \
+            apt-get install -y \
+                gcc-9-multilib \
+                g++-9-multilib \
+                libstdc++-11-dev:i386 \
+            ;; \
+        arm*) \
+            apt-get update && \
+            apt-get install -y \
+                libstdc++6 \
+                libc6 \
+            ;; \
+        *) \
+            echo "Unsupported TARGET_CONTAINER_BUILD_ARCH: $TARGET_CONTAINER_BUILD_ARCH" >&2 \
+            exit 1 \
+            ;; \
+    esac && \
+    rm -rf /var/lib/apt/lists/*
+
 USER user
 
 ENV CC=/usr/bin/clang-11 \
     CXX=/usr/bin/clang++-11 \
-    PATH=~/.local/bin:${PATH}
+    PATH=/home/user/.local/bin:${PATH}
 
 COPY docker-entrypoint.sh /
 CMD /docker-entrypoint.sh

docker/run_ubuntu-22.04/Dockerfile

@@ -1,18 +1,33 @@
 FROM ubuntu:22.04
 ENV DEBIAN_FRONTEND=noninteractive
-RUN \
-    dpkg --add-architecture i386 && \
-    apt-get update && \
+ARG TARGET_CONTAINER_PLATFORM
+
+# Base layer
+RUN apt-get update && \
     apt-get install -y --no-install-recommends \
         wget \
-        libstdc++6:i386 \
+        ca-certificates \
         tzdata \
         openssl \
-        libssl3 \
-        libssl-dev \
-    && \
+        python3 \
+        libatomic1 \
+        libstdc++6 \
+        libssl3 && \
+    rm -rf /var/lib/apt/lists/* && \
     useradd -m user
 
+# Arch-specific layer
+RUN case "$TARGET_CONTAINER_PLATFORM" in \
+        linux/amd64) \
+            dpkg --add-architecture i386 && \
+            apt-get update && \
+            apt-get install -y --no-install-recommends \
+                libstdc++6:i386 \
+                libssl3:i386 \
+            ;; \
+    esac && \
+    rm -rf /var/lib/apt/lists/*
+
 USER user
 WORKDIR /home/user