hack: add cross target

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

.dockerignore

@@ -1 +1,2 @@
 bin/
+cross-out/

Makefile

@@ -4,6 +4,9 @@ shell:
 binaries:
 	./hack/binaries
 
+binaries-cross:
+	EXPORT_LOCAL=cross-out ./hack/cross
+
 install: binaries
 	mkdir -p ~/.docker/cli-plugins
 	cp bin/buildx ~/.docker/cli-plugins/docker-buildx

hack/cross

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+. $(dirname $0)/util
+
+: ${TARGETPLATFORM=linux/amd64,linux/arm/v7,linux/arm64,darwin/amd64,windows/amd64,linux/ppc64le,linux/s390x}
+: ${CONTINUOUS_INTEGRATION=}
+: ${EXPORT_LOCAL=}
+
+set -ex
+
+exportFlag=""
+if [ -n "$EXPORT_LOCAL" ]; then
+	exportFlag="--output=type=local,dest=$EXPORT_LOCAL"
+fi
+
+progressFlag=""
+if [ "$CONTINUOUS_INTEGRATION" == "true" ]; then progressFlag="--progress=plain";
+fi
+
+buildctl build $progressFlag --frontend=dockerfile.v0 --local context=. --local dockerfile=. --opt platform=$TARGETPLATFORM $exportFlag --opt target=binaries