feat: add alpine-linux-arm64 build artifact

Add static binary build for arm64 architecture compatible with Alpine Linux
(musl libc). This enables dockerize usage in Alpine-based arm64 containers,
which is increasingly common with Apple Silicon and ARM cloud instances.

Changes:
- Makefile: add alpine-linux/arm64 build target with -tags netgo
- Makefile: add dockerize-alpine-linux-arm64 release tarball
- release.yml: add upload step for alpine-linux-arm64 asset

Author: Francisco Barón

.github/workflows/release.yml

@@ -52,6 +52,16 @@ jobs:
           asset_name: dockerize-alpine-linux-amd64-${{ steps.tag.outputs.tag }}.tar.gz
           asset_content_type: application/gzip
 
+      - name: Upload Alpine Linux ARM64
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ steps.create_release.outputs.upload_url }}
+          asset_path: ./dockerize-alpine-linux-arm64-${{ steps.tag.outputs.tag }}.tar.gz
+          asset_name: dockerize-alpine-linux-arm64-${{ steps.tag.outputs.tag }}.tar.gz
+          asset_content_type: application/gzip
+
       - name: Upload Alpine Linux PPC64LE
         uses: actions/upload-release-asset@v1
         env:

Makefile

@@ -20,6 +20,7 @@ dist-clean:
 
 dist: deps dist-clean
 	mkdir -p dist/alpine-linux/amd64 && GOOS=linux GOARCH=amd64 go build -ldflags "$(LDFLAGS)" -a -tags netgo -installsuffix netgo -o dist/alpine-linux/amd64/dockerize
+	mkdir -p dist/alpine-linux/arm64 && GOOS=linux GOARCH=arm64 go build -ldflags "$(LDFLAGS)" -a -tags netgo -installsuffix netgo -o dist/alpine-linux/arm64/dockerize
 	mkdir -p dist/alpine-linux/ppc64le && GOOS=linux GOARCH=ppc64le go build -ldflags "$(LDFLAGS)" -a -tags netgo -installsuffix netgo -o dist/alpine-linux/ppc64le/dockerize
 	mkdir -p dist/linux/amd64 && GOOS=linux GOARCH=amd64 go build -ldflags "$(LDFLAGS)" -o dist/linux/amd64/dockerize
 	mkdir -p dist/linux/386 && GOOS=linux GOARCH=386 go build -ldflags "$(LDFLAGS)" -o dist/linux/386/dockerize
@@ -34,6 +35,7 @@ dist: deps dist-clean
 
 release: dist
 	tar -cvzf dockerize-alpine-linux-amd64-$(TAG).tar.gz -C dist/alpine-linux/amd64 dockerize
+	tar -cvzf dockerize-alpine-linux-arm64-$(TAG).tar.gz -C dist/alpine-linux/arm64 dockerize
 	tar -cvzf dockerize-alpine-linux-ppc64le-$(TAG).tar.gz -C dist/alpine-linux/ppc64le dockerize
 	tar -cvzf dockerize-linux-amd64-$(TAG).tar.gz -C dist/linux/amd64 dockerize
 	tar -cvzf dockerize-linux-386-$(TAG).tar.gz -C dist/linux/386 dockerize