feat: build multi-architecture images in by default

This feature utilizes cross-compiling to generate binary files for
the amd64, s390x and arm64 architectures, followed by the creation
of images.

Signed-off-by: Nestor Acuna-Blanco <nestor.acuna@ibm.com>

Dockerfile

@@ -1,36 +1,43 @@
-FROM registry.access.redhat.com/ubi8/ubi-minimal as builder
-
-# create enviroment variables and files
-ENV ENVFILE=/tmp/envfile
-RUN echo "export ARCH=`uname -m | sed 's/x86_64/amd64/'`" >> ${ENVFILE}
-ENV PATH=$PATH:/usr/local/go/bin
+ARG TARGET_ARCH=amd64
+FROM registry.access.redhat.com/ubi8/ubi-minimal as base
+ARG TARGET_ARCH
 
+# download packages
 RUN microdnf install -y make tar gzip which && microdnf clean all
+RUN export ARCH=$(uname -m | sed 's/x86_64/amd64/'); curl -L https://go.dev/dl/go1.22.4.linux-${ARCH}.tar.gz | tar -C /usr/local -xzf -
+
+
+FROM base as builder
 
-RUN . ${ENVFILE}; curl -L https://go.dev/dl/go1.22.4.linux-${ARCH}.tar.gz | tar -C /usr/local -xzf -
+# in multistage builds the ARG must be renewed
+ARG TARGET_ARCH
 
+# create enviroment variables
+ENV PATH=$PATH:/usr/local/go/bin
+
+# copy the Go Modules manifests and vendor directory
 WORKDIR /workspace
-# Copy the Go Modules manifests and vendor directory
 COPY go.mod go.mod
 COPY go.sum go.sum
 COPY vendor/ vendor/
 
-# Copy the go source
+# copy the go source
 COPY Makefile Makefile
 COPY main.go main.go
 COPY api/ api/
 COPY pkg/ pkg/
 
-# Build
-RUN . ${ENVFILE}; CGO_ENABLED=0 GOOS=linux GOARCH=${ARCH} GO111MODULE=on make build
+# compile for the TARGET_ARCH
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=${TARGET_ARCH} make build
 
 
-FROM registry.access.redhat.com/ubi8/ubi-minimal
+FROM --platform=linux/${TARGET_ARCH} registry.access.redhat.com/ubi8/ubi-micro
 
-RUN microdnf update -y && microdnf clean all
+# in multistage builds the ARG must be renewed
+ARG TARGET_ARCH
 
+# copy binary from builder image
 WORKDIR /
 COPY --from=builder /workspace/bin/console .
 USER 1000
-
 ENTRYPOINT ["/console"]

Makefile

@@ -24,11 +24,14 @@ build: fmt vet
 
 .PHONY: build-container
 build-container: fmt vet test
-	podman build -t ${IMG} .
+	podman manifest rm ${IMG} || true && \
+	podman build --build-arg TARGET_ARCH=amd64 --manifest=${IMG} . && \
+	podman build --build-arg TARGET_ARCH=s390x --manifest=${IMG} . && \
+	podman build --build-arg TARGET_ARCH=arm64 --manifest=${IMG} .
 
 .PHONY: push-container
 push-container:
-	podman push ${IMG}
+	podman manifest push ${IMG}
 
 .PHONY: manifests
 manifests: