Add build specification

.drone.yml

@@ -14,3 +14,12 @@ steps:
       - mkdir -p $GOPATH/src/github.com/gluster
       - cd $GOPATH/src/github.com/gluster
       - git clone https://github.com/gluster/gluster-prometheus.git
+  - name: install deps
+    image: golang:alpine
+    commands:
+      - cd $GOPATH/src/github.com/gluster/gluster-prometheus
+      - ./scripts/install-reqs.sh
+  - name: build
+    image: golang:alpine
+    commands:
+      - PREFIX=/usr/local make