allow skip existing

tools/nuget-download-package/main.go

@@ -311,10 +311,16 @@ func main() {
 	log.Println("Using pkgVer " + pkgVer + " from " + targetUrl)
 
 	pkgBaseDir := filepath.Join(localRepoDir, pkgName, pkgVer)
+	if stat, err := os.Stat(filepath.Join(pkgBaseDir, "lib")); err == nil && stat.IsDir() {
+		log.Println(pkgBaseDir + "/lib already exists. This version has already been installed. Skipping the installation. ")
+		return
+	}
+
 	err := os.RemoveAll(pkgBaseDir)
 	logErrorIfAny(err, "rm -rf " + pkgBaseDir)
 	err = os.MkdirAll(pkgBaseDir, 0777)
 	logErrorIfAny(err, "mkdir -p " + pkgBaseDir)
+
 	if targetUrlLogin == "" {
 		httpGet(targetUrl, "", "", filepath.Join(pkgBaseDir, "openxt.pkgdown.zip"))
 	} else {