Nuget - building XF 3.6 framework to a different version

When I build XF 3.6 for NuGet with:

./Build.ps1 -Target NugetPack

I get :

========================================
_NuGetPack
========================================
Nuget Version: 3.6.0-3-6-0-0001

How can I change it to build version 9.9.9 instead?