Multiarch docker GitHub actions (#2065)

## Issue Addressed

Resolves #1512

## Proposed Changes

- Adds a new docker Github Actions workflow  
- Removes the Dockerhub hook
- Adds a new Dockerfile for use with pre-existing cross-compiled binaries 
- on pushes to `unstable` 
  - builds an ARM64 image and tags it `latest-arm64-unstable`
  - builds an AMD64 image and tags it `latest-amd64-unstable`
  - builds an multiarch image by creating a manifest list referencing the prior two images and tags it `latest-unstable`
- on pushes to `stable` 
  - builds an ARM64 image and tags it `latest-arm64`
  - builds an AMD64 image and tags it `latest-amd64`
  - builds an multiarch image by creating a manifest list referencing the prior two images and tags it `latest`

## Additional Info
- for ARM64, first `cross` is used to cross compile the `lighthouse` and  `lcli` binaries, then `docker buildx` is installed to actually build the docker image for the correct target platform. The image build pretty much just copies the binaries from local into the docker image (thanks @michaelsproul :) )
- The AMD64 and ARM64 builds run in parallel, in total it's been taking around 45mins on a local runner
- This PR does **not** cover version tags on docker images at the moment

Co-authored-by: realbigsean <seananderson33@gmail.com>

.github/workflows/docker.yml

@@ -0,0 +1,103 @@
+name: docker
+
+on:
+    push:
+        branches:
+            - unstable
+            - stable
+
+env:
+    DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
+    DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
+    IMAGE_NAME: sigp/lighthouse
+
+jobs:
+    extract-branch-name:
+        runs-on: ubuntu-latest
+        steps:
+            - name: Extract branch name
+              run: echo "::set-output name=BRANCH_NAME::$(echo ${GITHUB_REF#refs/heads/})"
+              id: extract_branch
+        outputs:
+            BRANCH_NAME: ${{ steps.extract_branch.outputs.BRANCH_NAME }}
+    build-docker-arm64:
+        runs-on: ubuntu-latest
+        needs: [extract-branch-name]
+        steps:
+            - uses: actions/checkout@v2
+            - name: Dockerhub login
+              run: |
+                  echo "${DOCKER_PASSWORD}" | docker login --username ${DOCKER_USERNAME} --password-stdin
+            - uses: actions-rs/toolchain@v1
+              with:
+                  toolchain: stable
+            - name: Cross build lighthouse binary
+              uses: actions-rs/cargo@v1
+              with:
+                  use-cross: true
+                  command: build
+                  args: --release --manifest-path lighthouse/Cargo.toml --target aarch64-unknown-linux-gnu --features portable
+            - name: Move cross-built ARM binary into Docker scope
+              run: |
+                  mkdir ./bin;
+                  mv ./target/aarch64-unknown-linux-gnu/release/lighthouse ./bin;
+            - name: Build Docker Buildx
+              run: |
+                  export DOCKER_BUILDKIT=1;
+                  docker build --platform=local -o . git://github.com/docker/buildx;
+                  mkdir -p ~/.docker/cli-plugins;
+                  mv buildx ~/.docker/cli-plugins/docker-buildx;
+            - name: Create Docker Builder
+              run: |
+                  docker run --rm --privileged multiarch/qemu-user-static --reset -p yes;
+                  docker context create builder;
+                  docker buildx create --use --name lighthouse builder;
+            - name: Set Env
+              if: needs.extract-branch-name.outputs.BRANCH_NAME == 'unstable'
+              run: |
+                  echo "TAG_SUFFIX=-unstable" >> $GITHUB_ENV;
+            - name: Build ARM64 dockerfile (with push)
+              run: |
+                  docker buildx build \
+                      --platform=linux/arm64 \
+                      --output "type=image,push=true" \
+                      --file ./Dockerfile.cross . \
+                      --tag ${IMAGE_NAME}:latest-arm64${TAG_SUFFIX}
+    build-docker-amd64:
+        runs-on: ubuntu-latest
+        needs: [extract-branch-name]
+        steps:
+            - uses: actions/checkout@v2
+            - name: Dockerhub login
+              run: |
+                  echo "${DOCKER_PASSWORD}" | docker login --username ${DOCKER_USERNAME} --password-stdin
+            - name: Set Env
+              if: needs.extract-branch-name.outputs.BRANCH_NAME == 'unstable'
+              run: |
+                  echo "TAG_SUFFIX=-unstable" >> $GITHUB_ENV;
+            - name: Build AMD64 dockerfile (with push)
+              run: |
+                  docker build \
+                      --build-arg PORTABLE=true \
+                      --tag ${IMAGE_NAME}:latest-amd64${TAG_SUFFIX} \
+                      --file ./Dockerfile .
+                  docker push ${IMAGE_NAME}:latest-amd64${TAG_SUFFIX}
+    build-docker-multiarch:
+        runs-on: ubuntu-latest
+        needs: [build-docker-arm64, build-docker-amd64, extract-branch-name]
+        steps:
+            - name: Dockerhub login
+              run: |
+                  echo "${DOCKER_PASSWORD}" | docker login --username ${DOCKER_USERNAME} --password-stdin
+            - name: Set Env
+              if: needs.extract-branch-name.outputs.BRANCH_NAME == 'unstable'
+              run: |
+                  echo "TAG_SUFFIX=-unstable" >> $GITHUB_ENV;
+            - name: Create and push multiarch manifest
+                # We need to enable experimental docker features in order to use `docker manifest`
+              run: |
+                  export DOCKER_CLI_EXPERIMENTAL=enabled;
+                  docker manifest create ${IMAGE_NAME}:latest${TAG_SUFFIX} \
+                      --amend ${IMAGE_NAME}:latest-arm64${TAG_SUFFIX} \
+                      --amend ${IMAGE_NAME}:latest-amd64${TAG_SUFFIX};
+                  docker manifest push ${IMAGE_NAME}:latest${TAG_SUFFIX}

Dockerfile.cross

@@ -0,0 +1,10 @@
+# This image is meant to enable cross-architecture builds.
+# It assumes the lighthouse binary has already been
+# compiled for `$TARGETPLATFORM` and moved to `./bin`.
+FROM --platform=$TARGETPLATFORM debian:buster-slim
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  libssl-dev \
+  ca-certificates \
+  && apt-get clean \
+  && rm -rf /var/lib/apt/lists/*
+COPY ./bin/lighthouse /usr/local/bin/lighthouse

hooks/build

@@ -1,4 +0,0 @@
-#!/bin/bash
-
-# Build hook to run on Docker Hub to ensure that the image is built with `PORTABLE=true`.
-docker build --build-arg PORTABLE=true -f $DOCKERFILE_PATH -t $IMAGE_NAME .