build: fix docker multiarch build

Dockerfile

@@ -1,5 +1,3 @@
-ARG TARGETOS=linux
-ARG TARGETARCH=amd64
 ARG LDFLAGS
 ARG VERSION
 
@@ -17,7 +15,7 @@ COPY . /workspace
 
 ### Core
 FROM build AS build
-RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="${LDFLAGS}" -o /out/runner cmd/streaming/*.go
+RUN CGO_ENABLED=0 go build -ldflags="${LDFLAGS}" -o /out/runner cmd/streaming/*.go
 
 FROM gcr.io/distroless/static:nonroot as runner
 ARG VERSION

Makefile

@@ -71,9 +71,11 @@ LDFLAGS += -X main.version=$(VERSION)
 build: fmt lint ## Build core binary.
 	go build -ldflags="${LDFLAGS}" -a -o bin/runner cmd/streaming/*
 
+DOCKER_BUILD_FLAGS ?= --load
+
 .PHONY: docker-build
 docker-build: ## Build docker image with the Runner.
-	DOCKER_BUILDKIT=1 docker build --build-arg LDFLAGS="${LDFLAGS}" --build-arg VERSION="${VERSION}" -t ${IMAGE_BASE}:${VERSION} -t ${IMAGE_BASE}:latest .
+	docker buildx build ${DOCKER_BUILD_FLAGS} --build-arg LDFLAGS="${LDFLAGS}" --build-arg VERSION="${VERSION}" -t ${IMAGE_BASE}:${VERSION} -t ${IMAGE_BASE}:latest .
 
 .PHONY: kind-load
 kind-load: ## Load the runner into kind.