Add Alpine Linux images (#745)

* Add Alpine Linux images.

Fixes #453
Fixes #528

* Move Dockerfiles to build directory.

.goreleaser.yml

@@ -55,10 +55,16 @@ changelog:
     - Merge branch
 
 dockers:
-  - image_templates:
+  - dockerfile: build/Dockerfile
+    image_templates:
       - "golangci/golangci-lint:latest"
       - "golangci/golangci-lint:{{ .Tag }}"
       - "golangci/golangci-lint:v{{ .Major }}.{{ .Minor }}"
+  - dockerfile: build/Dockerfile.alpine
+    image_templates:
+      - "golangci/golangci-lint:latest-alpine"
+      - "golangci/golangci-lint:{{ .Tag }}-alpine"
+      - "golangci/golangci-lint:v{{ .Major }}.{{ .Minor }}-alpine"
 
 brews:
   - github:

build/Dockerfile.alpine

@@ -0,0 +1,8 @@
+FROM golang:1.13-alpine
+
+# required to support cgo
+RUN apk --no-cache add gcc musl-dev
+
+# don't place it into $GOPATH/bin because Drone mounts $GOPATH as volume
+COPY golangci-lint /usr/bin/
+CMD ["golangci-lint"]