Simplify alpine Dockerfile

Author: ernado

build/Dockerfile.alpine

@@ -1,10 +1,9 @@
 FROM golang:1.13-alpine
 
-# required to support cgo
-RUN apk --no-cache add gcc musl-dev
-
-# needed most times for `go get`, etc. See https://github.com/docker-library/golang/issues/80
-RUN apk add --no-cache git mercurial
+# gcc is required to support cgo;
+# git and mercurial are needed most times for go get`, etc.
+# See https://github.com/docker-library/golang/issues/80
+RUN apk --no-cache add gcc musl-dev git mercurial
 
 # don't place it into $GOPATH/bin because Drone mounts $GOPATH as volume
 COPY golangci-lint /usr/bin/