wip: build linux/arm64 docker images

.github/workflows/docker.yml

@@ -69,3 +69,46 @@ jobs:
       - name: Inspect Docker images
         run: |
           docker images
+
+  docker-build-toolchain:
+    needs: [prepare]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ (inputs.commit != '' && inputs.commit) || inputs.branch }}
+      - name: Download toolchain
+        uses: dawidd6/action-download-artifact@v3
+        with:
+          workflow: build.yml
+          workflow_conclusion: success
+          commit: ${{inputs.commit}}
+          branch: ${{inputs.branch}}
+          event: push
+          name: linux-ucrt-.*
+          name_is_regexp: true
+          path: toolchain
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Log in to Docker Hub
+        if: ${{inputs.login}}
+        uses: docker/login-action@v3
+        with:
+          username: ${{secrets.DOCKER_USERNAME}}
+          password: ${{secrets.DOCKER_PASSWORD}}
+      - name: Build Docker images
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/arm64
+          push: ${{inputs.push}}
+          file: ./Dockerfile.toolchain
+          load: true
+          tags: |
+            mstorsjo/llvm-mingw:latest
+            mstorsjo/llvm-mingw:${{needs.prepare.outputs.TAG}}
+      - name: Inspect Docker images
+        run: |
+          docker images

.gitignore

@@ -5,3 +5,4 @@
 /libffi
 /cpython*
 /python-native
+/toolchain

Dockerfile.toolchain

@@ -0,0 +1,41 @@
+FROM ubuntu:20.04
+
+RUN apt-get update -qq && \
+    DEBIAN_FRONTEND="noninteractive" apt-get install -qqy --no-install-recommends \
+    git wget bzip2 file unzip libtool pkg-config cmake build-essential \
+    automake yasm gettext autopoint vim-tiny python3 python3-distutils \
+    ninja-build ca-certificates curl less zip && \
+    apt-get clean -y && \
+    rm -rf /var/lib/apt/lists/*
+
+# Manually install a newer version of CMake; this is needed since building
+# LLVM requires CMake 3.20, while Ubuntu 20.04 ships with 3.16.3. If
+# updating to a newer distribution, this can be dropped.
+RUN cd /opt && \
+    curl -LO https://github.com/Kitware/CMake/releases/download/v3.26.4/cmake-3.26.4-Linux-$(uname -m).tar.gz && \
+    tar -zxf cmake-*.tar.gz && \
+    rm cmake-*.tar.gz && \
+    mv cmake-* cmake
+ENV PATH=/opt/cmake/bin:$PATH
+
+
+RUN git config --global user.name "LLVM MinGW" && \
+    git config --global user.email root@localhost
+
+WORKDIR /build
+
+ENV TOOLCHAIN_PREFIX=/opt/llvm-mingw
+
+ARG TOOLCHAIN_ARCHS="i686 x86_64 armv7 aarch64"
+
+# Copy prebuilt toolchains for the current architecture.
+# Test executing a binary, to make sure that it works (i.e. it is not built
+# requiring a newer version of glibc or libstdc++ than what is available in
+# this container).
+RUN --mount=type=bind,source=toolchain,target=/toolchain \
+    mkdir -p $TOOLCHAIN_PREFIX && ARCH=$(uname -m) && \
+    tar xf /toolchain/linux-ucrt-$ARCH-toolchain/llvm-mingw-*-$ARCH.tar.xz --strip-components 1 -C $TOOLCHAIN_PREFIX && \
+    ANY_ARCH=$(echo $TOOLCHAIN_ARCHS | awk '{print $1}') && \
+    $TOOLCHAIN_PREFIX/bin/$ANY_ARCH-w64-mingw32-clang --version
+
+ENV PATH=$TOOLCHAIN_PREFIX/bin:$PATH