fix: multiarch docker image (#423)

* fix: multiarch docker image

* fix: remove binutils gold

* fix: add binutils gold to xx-apk

* fix: add binutils to xx-apk

* fix: remove binutils to xx-apk

* fix: try refactoring Dockerfile and see if CI runs successfully

* fix: add binutils-gold

* fix: add binutils-gold explicit version

* fix: add binutils-gold explicit version

* fix: add binutils-cross

* fix: add binutils with explicit version

* fix: bump build-push-action, remove cache

* fix: remove cache

* fix: add qemu to github actions

* fix: update github actions

* fix: switch to debian based builder platform

* fix: arrange Dockerfile.backend

* documentation: add comment

* refactor: move CGO to env, wrap go, remove mounts

* fix: pass static flag to external linker

Dockerfile.backend

@@ -7,9 +7,18 @@ COPY ui .
 RUN npm i
 RUN npm run build
 
-FROM --platform=$BUILDPLATFORM golang:1.20.5-alpine AS builder
+# xx is a helper for cross-compilation
+FROM --platform=$BUILDPLATFORM tonistiigi/xx:1.2.1@sha256:8879a398dedf0aadaacfbd332b29ff2f84bc39ae6d4e9c0a1109db27ac5ba012 AS xx
 
-RUN apk add --update --no-cache gcc g++ git binutils-gold
+FROM --platform=$BUILDPLATFORM golang:1.20.5-bullseye AS builder
+
+COPY --from=xx / /
+
+ARG TARGETPLATFORM
+
+RUN apt-get update && xx-apt-get install -y --no-install-recommends gcc libc6-dev
+
+RUN xx-go --wrap
 
 # Copy vmclarity code to /build
 COPY . /build
@@ -20,17 +29,16 @@ WORKDIR /build/backend
 ARG VERSION
 ARG BUILD_TIMESTAMP
 ARG COMMIT_HASH
-ARG TARGETOS
-ARG TARGETARCH
 
-RUN --mount=type=cache,target=/go/pkg/mod \
-    --mount=type=cache,target=/root/.cache/go-build \
-    GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
-    go build -ldflags="-s -w \
+ENV CGO_ENABLED=1
+
+RUN go build -ldflags="-s -w -extldflags -static \
      -X 'github.com/openclarity/vmclarity/backend/pkg/version.Version=${VERSION}' \
      -X 'github.com/openclarity/vmclarity/backend/pkg/version.CommitHash=${COMMIT_HASH}' \
      -X 'github.com/openclarity/vmclarity/backend/pkg/version.BuildTimestamp=${BUILD_TIMESTAMP}'" -o backend ./cmd/backend/main.go
 
+RUN xx-verify backend
+
 FROM alpine:3.18
 
 WORKDIR /app