Updated Dockerfile for arm64 build

Signed-off-by: Roberto Bonafiglia <[email protected]>

Dockerfile

@@ -1,8 +1,12 @@
 ARG BCI_IMAGE=registry.suse.com/bci/bci-base
 ARG GO_IMAGE=rancher/hardened-build-base:v1.21.9b1
-FROM ${BCI_IMAGE} as bci
-FROM ${GO_IMAGE} as builder
+FROM --platform=$BUILDPLATFORM tonistiigi/xx AS xx
+FROM --platform=$TARGETPLATFORM ${BCI_IMAGE} as bci
+FROM --platform=$TARGETPLATFORM ${GO_IMAGE} as builder
 # setup required packages
+COPY --from=xx / /
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
 RUN set -x && \
     apk --no-cache add \
     file \
@@ -11,9 +15,11 @@ RUN set -x && \
     linux-headers \
     make
 # setup the build
-ARG ARCH="amd64"
 ARG K3S_ROOT_VERSION=v0.13.0
-ADD https://github.com/rancher/k3s-root/releases/download/${K3S_ROOT_VERSION}/k3s-root-xtables-${ARCH}.tar /opt/xtables/k3s-root-xtables.tar
+RUN xx-info env
+RUN mkdir -p /opt/xtables/
+RUN export ARCH=$(xx-info arch) &&\
+    wget https://github.com/rancher/k3s-root/releases/download/${K3S_ROOT_VERSION}/k3s-root-xtables-${ARCH}.tar -O /opt/xtables/k3s-root-xtables.tar
 RUN tar xvf /opt/xtables/k3s-root-xtables.tar -C /opt/xtables
 ARG TAG=v0.25.1
 ARG PKG="github.com/flannel-io/flannel"
@@ -24,9 +30,15 @@ RUN git fetch --all --tags --prune
 RUN git checkout tags/${TAG} -b ${TAG}
 # build and assert statically linked executable(s)
 ENV GO_LDFLAGS="-X ${PKG}/version.Version=${TAG}"
-RUN go-build-static.sh -gcflags=-trimpath=${GOPATH}/src -o bin/flanneld .
-RUN go-assert-static.sh bin/*
-RUN if [ "${ARCH}" = "amd64" ]; then \
+RUN export GOOS=$(xx-info os) &&\
+    export GOARCH=$(xx-info arch) &&\
+    export ARCH=$(xx-info arch) &&\
+    go-build-static.sh -gcflags=-trimpath=${GOPATH}/src -o bin/flanneld .
+RUN export GOOS=$(xx-info os) &&\
+    export GOARCH=$(xx-info arch) &&\
+    export ARCH=$(xx-info arch) &&\
+    go-assert-static.sh bin/*
+RUN if [ "$(xx-info arch)" = "amd64" ]; then \
         go-assert-boring.sh bin/* ; \
     fi
 RUN install -s bin/* /usr/local/bin