Merge pull request #13 from pfnet-research/fix-multi-arch

Fix a failure to build arm64 image

.github/workflows/ci.yaml

@@ -20,4 +20,4 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - run: make docker-build
+    - run: make docker-build-all

Dockerfile

@@ -1,5 +1,5 @@
 # syntax = docker/dockerfile:1
-FROM golang:1.18 AS base
+FROM --platform=$BUILDPLATFORM golang:1.18 AS base
 WORKDIR /workspace
 ENV CGO_ENABLED=0
 COPY go.* .
@@ -31,7 +31,7 @@ RUN --mount=target=. \
 FROM scratch AS export
 COPY --from=build /out/alertmanager-to-github /
 
-FROM gcr.io/distroless/static:nonroot-${TARGETARCH}
+FROM --platform=$BUILDPLATFORM gcr.io/distroless/static:nonroot
 COPY --from=build /out/alertmanager-to-github /
 ENTRYPOINT ["/alertmanager-to-github"]
 CMD ["start"]