use buildx to speedup arm builds

Signed-off-by: Matthias Bertschy <matthias.bertschy@gmail.com>

build/Dockerfile

@@ -1,21 +1,21 @@
-FROM golang:1.20-alpine as builder
+FROM --platform=$BUILDPLATFORM golang:1.20-alpine as builder
 
 ENV GO111MODULE=on CGO_ENABLED=0
 WORKDIR /work
+ARG TARGETOS TARGETARCH
 
-ADD go.mod go.sum /work/
-RUN go mod download
-
-ADD . .
-RUN go build -o build/kubevuln cmd/http/main.go
+RUN --mount=target=. \
+    --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=cache,target=/go/pkg \
+    GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o /out/kubevuln cmd/http/main.go
 
 FROM alpine
 
 RUN addgroup -S ks && adduser -S ks -G ks
 USER ks
 WORKDIR /home/ks/
 
-COPY --from=builder /work/build/kubevuln /usr/bin/kubevuln
+COPY --from=builder /out/kubevuln /usr/bin/kubevuln
 
 ARG image_version
 ENV RELEASE=$image_version

build/README.md

@@ -9,5 +9,5 @@ git clone https://github.com/kubescape/kubevuln.git kubevuln && cd "$_"
 
 2. Build
 ```
-docker build -t kubevuln -f build/Dockerfile .
-```
+docker buildx build -t kubevuln -f build/Dockerfile --load .
+```