Add docker image that can be used to build projects with wasi-sdk sysroot

.dockerignore

@@ -1,3 +1,3 @@
-# We don't need any files to for build image.
-# Without this `docker build` will everything in this directory.
-*
+# Our docker builds do not require the submodule sources so exclude them as
+# they can be very big.
+/src

.github/workflows/main.yml

@@ -7,6 +7,7 @@ on:
     branches:
       - main
   pull_request:
+  workflow_dispatch:
 
 jobs:
   build:
@@ -93,6 +94,27 @@ jobs:
       - uses: actions/checkout@v1
         with:
           submodules: true
+
+      - uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: docker/setup-qemu-action@v2
+      - uses: docker/setup-buildx-action@v2
+
+      - uses: docker/metadata-action@v4
+        id: meta
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=schedule
+            type=ref,event=branch
+            type=ref,event=tag
+            type=ref,event=pr
+            type=sha
+
       - name: Run docker_build script
         run: ./docker_build.sh
       - name: Upload artifacts
@@ -101,3 +123,15 @@ jobs:
           # Upload the dist folder. Give it a name according to the OS it was built for.
           name: dist-ubuntu-xenial
           path: dist
+
+      - name: Build and push wasi-sdk docker image
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          file: docker/Dockerfile
+          push: ${{ github.event_name != 'pull_request' }}
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

docker/Dockerfile

@@ -0,0 +1,54 @@
+# Docker image with a build toolchain and environment variables set to use
+# the wasi-sdk sysroot. The SDK distribution must have first been built,
+# for example using docker_build.sh
+
+# Extract built SDK archive to copy out the sysroot. We use an initial build
+# stage to do this to make sure it is only the sysroot, not the entire SDK
+# with binaries, that is included in the final image since we install those
+# separately.
+FROM ubuntu:22.04 as dist
+
+ADD dist/wasi-sdk-*.*-linux.tar.gz /
+
+# Move versioned folder to unversioned to using bash glob to allow
+# this file to be independent of major version number.
+RUN mv /wasi-sdk-* /wasi-sdk
+
+FROM ubuntu:22.04
+
+ENV LLVM_VERSION 15
+
+# Install build toolchain including clang, ld, make, autotools, ninja, and cmake
+RUN apt-get update && \
+    # Temporarily install to setup apt repositories
+    apt-get install -y curl gnupg && \
+\
+    curl -sS https://apt.llvm.org/llvm-snapshot.gpg.key | gpg --dearmor > /etc/apt/trusted.gpg.d/llvm.gpg && \
+    echo "deb [signed-by=/etc/apt/trusted.gpg.d/llvm.gpg] http://apt.llvm.org/jammy/ llvm-toolchain-jammy-${LLVM_VERSION} main" >> /etc/apt/sources.list.d/llvm.list && \
+    echo "deb-src [signed-by=/etc/apt/trusted.gpg.d/llvm.gpg] http://apt.llvm.org/jammy/ llvm-toolchain-jammy-${LLVM_VERSION} main" >> /etc/apt/sources.list.d/llvm.list && \
+\
+    apt-get update && \
+    apt-get install -y clang-${LLVM_VERSION} lld-${LLVM_VERSION} cmake ninja-build make autoconf autogen automake libtool && \
+    apt-get remove -y curl gnupg && \
+    rm -rf /var/lib/apt/lists/*
+
+COPY --from=dist /wasi-sdk/share/wasi-sysroot/ /wasi-sysroot/
+# The path to the rt directory contains the LLVM patch version which is not reflected in the LLVM apt repository
+# or package. To make adding the RT robust to changing patch versions without needing to duplicate the folder
+# content, we symlink after extracting using a bash glob to resolve the patch version
+ADD dist/libclang_rt.builtins-wasm32-wasi-*.*.tar.gz /wasi-sysroot-clang_rt
+RUN ln -s /wasi-sysroot-clang_rt/lib/wasi/ $(echo /usr/lib/llvm-${LLVM_VERSION}/lib/clang/${LLVM_VERSION}.*)/lib/wasi
+
+ADD docker/wasi-sdk.cmake /usr/share/cmake/wasi-sdk.cmake
+ENV CMAKE_TOOLCHAIN_FILE /usr/share/cmake/wasi-sdk.cmake
+ADD cmake/Platform/WASI.cmake /usr/share/cmake/Modules/Platform/WASI.cmake
+
+ENV CC clang-${LLVM_VERSION}
+ENV CXX clang++-${LLVM_VERSION}
+ENV LD wasm-ld-${LLVM_VERSION}
+ENV AR llvm-ar-${LLVM_VERSION}
+ENV RANLIB llvm-ranlib-${LLVM_VERSION}
+
+ENV CFLAGS --target=wasm32-wasi --sysroot=/wasi-sysroot
+ENV CXXFLAGS --target=wasm32-wasi --sysroot=/wasi-sysroot -fno-exceptions
+ENV LDFLAGS --target=wasm32-wasi --sysroot=/wasi-sysroot

docker/wasi-sdk.cmake

@@ -0,0 +1,27 @@
+# Cmake toolchain description file for the wasi-sdk docker image
+
+# This is arbitrary, AFAIK, for now.
+cmake_minimum_required(VERSION 3.4.0)
+
+# To make sure it recognizes the WASI platform
+list(APPEND CMAKE_MODULE_PATH /usr/share/cmake/Modules)
+
+set(CMAKE_SYSTEM_NAME WASI)
+set(CMAKE_SYSTEM_VERSION 1)
+set(CMAKE_SYSTEM_PROCESSOR wasm32)
+set(triple wasm32-wasi)
+
+set(CMAKE_C_COMPILER /usr/bin/clang-15)
+set(CMAKE_CXX_COMPILER /usr/bin/clang++-15)
+set(CMAKE_AR /usr/bin/llvm-ar-15)
+set(CMAKE_RANLIB /usr/bin/llvm-ranlib-15)
+set(CMAKE_C_COMPILER_TARGET ${triple})
+set(CMAKE_CXX_COMPILER_TARGET ${triple})
+SET(CMAKE_SYSROOT /wasi-sysroot)
+
+# Don't look in the sysroot for executables to run during the build
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+# Only look in the sysroot (not in the host paths) for the rest
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)