Reverted change in base image; Added 'promu' in Dockerfile

Author: carlosadiegosysdig

Dockerfile

@@ -1,6 +1,9 @@
-ARG ARCH="amd64"
-ARG OS="linux"
-FROM quay.io/prometheus/busybox-${OS}-${ARCH}:glibc
+FROM quay.io/prometheus/golang-builder as builder
+
+ARG PROMU_VERSION=0.13.0
+RUN curl -LJO https://github.com/prometheus/promu/releases/download/v${PROMU_VERSION}/promu-${PROMU_VERSION}.linux-amd64.tar.gz 
+RUN tar -xvzf promu-${PROMU_VERSION}.linux-amd64.tar.gz 
+RUN mv promu-${PROMU_VERSION}.linux-amd64/promu /go/bin
 
 ADD .   /go/src/github.com/prometheus-community/elasticsearch_exporter
 WORKDIR /go/src/github.com/prometheus-community/elasticsearch_exporter