This tool can be used to generate response files for 64 bit NSL msi. These files get generated in C:\NSLFiles as responsefile.ini. These can be further used as mentioned in NSL documentation to silently install NSL.
Disclaimer: As with everything else at NetIQ Cool Solutions, this content is definitely not supported by NetIQ, so Customer Support will not be able to help you if it has any adverse effect on your environment. It just worked for at least one person, and perhaps it will be useful for you too. Be sure to test in a non-production environment.