arm build fix

Dockerfile.arm

@@ -3,10 +3,10 @@ RUN apk add --update musl-dev gcc go git mercurial bash wget ca-certificates
 RUN mkdir -p /go/src/github.com/kpmy/mipfs
 COPY . /go/src/github.com/kpmy/mipfs
 ENV GOPATH /go
-ENV GOBIN /usr/bin
 RUN go get -v github.com/kpmy/mipfs/dav_cmd
 RUN go install github.com/kpmy/mipfs/dav_cmd
 RUN mkdir -p /go/.diskv
 RUN printf "ipfs:5001" > /go/.diskv/ipfs
 EXPOSE 6001
-CMD dav_cmd
+WORKDIR /go
+CMD /go/bin/dav_cmd