Add Dockerfile.arm for arm based devices (#70)

This will for example work with Raspberry Pi

Author: tsvehagen

Dockerfile.arm

@@ -0,0 +1,20 @@
+FROM arm32v6/golang:1.9-alpine3.6 AS development
+
+ENV PROJECT_PATH=/go/src/github.com/brocaar/lora-gateway-bridge
+ENV PATH=$PATH:$PROJECT_PATH/build
+
+RUN apk add --no-cache ca-certificates make git bash
+
+RUN mkdir -p $PROJECT_PATH
+COPY . $PROJECT_PATH
+WORKDIR $PROJECT_PATH
+
+RUN make requirements
+RUN make GOARCH=arm
+
+FROM alpine:latest AS production
+
+WORKDIR /root/
+RUN apk --no-cache add ca-certificates
+COPY --from=development /go/src/github.com/brocaar/lora-gateway-bridge/build/lora-gateway-bridge .
+ENTRYPOINT ["./lora-gateway-bridge"]