[docker] Add multi arch support with default support for amd64 and optional support for arm32v6

Author: Fohlen

Dockerfile

@@ -1,4 +1,10 @@
-FROM golang:1.10.0 AS builder
+ARG ARCH=amd64
+
+FROM golang:1.10.0 AS builder-amd64
+
+FROM arm32v6/golang:1.10.0 AS builder-arm32v6
+
+FROM builder-${ARCH} AS builder
 
 WORKDIR ${GOPATH}/src/github.com/mcuadros/ofelia
 COPY . ${GOPATH}/src/github.com/mcuadros/ofelia
@@ -16,4 +22,4 @@ COPY --from=builder /go/bin/ofelia /usr/bin/ofelia
 VOLUME /etc/ofelia/
 ENTRYPOINT ["/usr/bin/ofelia"]
 
-CMD ["daemon", "--config", "/etc/ofelia/config.ini"]
+CMD ["daemon", "--config", "/etc/ofelia/config.ini"]