CI: Add export-version command (#55072)

* Add export-version command

* Fix lint

* 1-line cleanup

pkg/build/cmd/exportversion.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/urfave/cli/v2"
+)
+
+func ExportVersion(c *cli.Context) error {
+	metadata, err := GenerateMetadata(c)
+	if err != nil {
+		return err
+	}
+
+	const distDir = "dist"
+	if err := os.RemoveAll(distDir); err != nil {
+		return err
+	}
+	if err := os.Mkdir(distDir, 0750); err != nil {
+		return err
+	}
+
+	// nolint:gosec
+	if err := os.WriteFile(filepath.Join(distDir, "grafana.version"), []byte(metadata.GrafanaVersion), 0664); err != nil {
+		return err
+	}
+
+	return nil
+}