Building with librdkafka 1.6+ doesn't require librdkafka library any more (#67)

* "-tags static" makes the package re-distributable without requiring librdkafka on the receiving host

* mention librdkafka requirement in build as well

* don't do apt step at all

* don't require librdkafka during build in docs either

* revert static build change

Author: johnseekins

Dockerfile

@@ -1,6 +1,4 @@
-FROM golang:1.16.1-buster as build
-
-RUN apt update && apt install build-essential -y
+FROM golang:1.16.3-buster as build
 
 WORKDIR /src/prometheus-kafka-adapter
 

README.md

@@ -78,8 +78,6 @@ When deployed in a Kubernetes cluster using Helm and using an external Prometheu
 
 ## development
 
-Building requires librdkafka be available on the building host. It is typically available in distribution package archives, but can also be downloaded and built from here: https://github.com/edenhill/librdkafka.git
-
 ```
 go test
 go build