docker: Add ARM docker container dockerfile. (#3574)

Dockerfile.armhf

@@ -0,0 +1,18 @@
+FROM resin/armhf-alpine:3.5
+
+ENV GOPATH /go
+ENV PATH $PATH:$GOPATH/bin
+ENV CGO_ENABLED 0
+
+WORKDIR /go/src/github.com/minio/
+
+RUN  \
+     apk add --no-cache --virtual .build-deps git go musl-dev ca-certificates && \
+     go get -v -d github.com/minio/minio && \
+     cd /go/src/github.com/minio/minio && \
+     go install -v -ldflags "$(go run buildscripts/gen-ldflags.go)" && \
+     rm -rf /go/pkg /go/src /usr/local/go && apk del .build-deps
+
+EXPOSE 9000
+ENTRYPOINT ["minio"]
+VOLUME ["/export"]