support for multiarch docker manifest

merged from https://github.com/klutchell/cloudflared
requires 'docker login' prior to 'make manifest' so the image can be pushed

Dockerfile

@@ -1,12 +1,22 @@
-FROM golang:1.12 as builder
-WORKDIR /go/src/github.com/cloudflare/cloudflared/
-RUN apt-get update && apt-get install -y --no-install-recommends upx
-# Run after `apt-get update` to improve rebuild scenarios
-COPY . .
-RUN make cloudflared
-RUN upx --no-progress cloudflared
+FROM golang:1.12-alpine as builder
+
+WORKDIR /go/src/github.com/cloudflare/cloudflared/
+
+COPY . .
+
+ENV GO111MODULE on
+ENV CGO_ENABLED 0
+
+RUN apk add --no-cache build-base=0.5-r1 git=2.22.0-r0 upx=3.95-r2 \
+    && make cloudflared \
+    && upx --no-progress cloudflared
+
+FROM scratch
 
-FROM gcr.io/distroless/base
 COPY --from=builder /go/src/github.com/cloudflare/cloudflared/cloudflared /usr/local/bin/
+
 ENTRYPOINT ["cloudflared", "--no-autoupdate"]
+
 CMD ["version"]
+
+RUN ["cloudflared", "--version"]

Makefile

@@ -6,6 +6,8 @@ IMPORT_PATH   := github.com/cloudflare/cloudflared
 PACKAGE_DIR   := $(CURDIR)/packaging
 INSTALL_BINDIR := usr/local/bin
 
+DOCKER_CLI_EXPERIMENTAL := enabled
+
 EQUINOX_FLAGS = --version="$(VERSION)" \
 				 --platforms="$(EQUINOX_BUILD_PLATFORMS)" \
 				 --app="$(EQUINOX_APP_ID)" \
@@ -35,6 +37,17 @@ cloudflared: tunnel-deps
 container:
 	docker build -t cloudflare/cloudflared:"$(VERSION)" .
 
+.PHONY: manifest
+manifest:
+	docker run --rm --privileged aptman/qus -s -- -r
+	docker run --rm --privileged aptman/qus -s -- -p
+	-docker buildx create --use --name cloudflared
+	docker buildx inspect --bootstrap
+	docker buildx build . \
+		-t cloudflare/cloudflared:"$(VERSION)" \
+		--platform=linux/amd64,linux/arm64,linux/386,linux/arm/v7,linux/arm/v6 \
+		--pull --push
+
 .PHONY: test
 test: vet
 	go test -v -mod=vendor -race $(VERSION_FLAGS) ./...