Clarified pre-requisites for bootstrap scripts

Clarified pre-requisites for bootstrap scripts

Author: negust-microsoft

samples/features/sql-big-data-cluster/README.md

@@ -3,7 +3,7 @@
 ## Pre-requisites
 1. Kubernetes cluster configuration & Kubectl command-line utility
 2. Curl utility
-3. Sqlcmd utility
+3. Sqlcmd utility (Installation instructions [here for Linux](https://docs.microsoft.com/en-us/sql/linux/sql-server-linux-setup-tools?view=sql-server-ver15) and [here for Windows](https://www.microsoft.com/en-us/download/details.aspx?id=53591 download))
 4. Bcp utility
 5. Azure Data Studio or SQL Server Management Studio
 6. SQL Server 2019 big data cluster