Make version a var and add arr_build.sh

By change Version from and const to a var we are able to use
ldflags to set the version dynamically.

In the arr_build.sh file for example, we can set it with:
-ldflags="-X go.mozilla.org/sops/v3/version.Version=$VERSION"

arr_build.sh will buld the sops binary in the repo root
and will print the instructions for releasing it to gcs.

arr_build.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -e
+VERSION=$(git describe) 
+VERSION="${VERSION:1}" # change example v3.7.1 to 3.7.1
+go build -o sops -ldflags="-X go.mozilla.org/sops/v3/version.Version=$VERSION" ./cmd/sops 
+
+echo "Successfully built with version: $(./sops --version)"
+
+BUCKET=arrikto
+OBJECT=sops/sops-${VERSION}
+GSURL=gs://${BUCKET}/${OBJECT}
+URL=https://storage.googleapis.com/${BUCKET}/${OBJECT}
+
+echo To upload to GCS run:
+echo "  gsutil cp ./sops ${GSURL}"
+
+echo To make it public run:
+echo "  gsutil acl ch -u AllUsers:R ${GSURL}"
+
+echo To verify that it is publicly accessible run:
+echo "  curl -I ${URL}"
+

version/version.go

@@ -11,7 +11,7 @@ import (
 )
 
 // Version represents the value of the current semantic version
-const Version = "3.7.1"
+var Version = "3.7.1"
 
 // PrintVersion handles the version command for sops
 func PrintVersion(c *cli.Context) {