The build process has changed a lot since 9.3.0, so it will depend somewhat on what version you're building against. For the latest version (since 9.5.0), you can run ./build.ps1 --target=CreateSettings which will generate a setting.local.json file. In that file, version will be set to "auto", which will use information for the Git repository and branch to determine the version. You can change this to be a specific version (e.g. "9.9.1").  After that's set, ./build.ps1 will do a full build and produce packages in the Artifacts folder that you can use to install a site.

For older versions I believe you'll want to add version info to SolutionInfo.cs. There's also an AssemblyStatus attribute in DNN Platform/Library/Properties/AssemblyInfo.cs that you may want to change.

Hope it helps,

Thank you for the detailed answer that put me on the right track!

If someone will get error message like "Could not download NuGet.exe" after the command "./build.ps1 --target=CreateSettings", please make sure that PowerShell is using correct encryption. For me following code snippet did the trick. 

 try {

    # Set TLS 1.2 (3072), then TLS 1.1 (768), then TLS 1.0 (192), finally SSL 3.0 (48)

    # Use integers because the enumeration values for TLS 1.2 and TLS 1.1 won't

    # exist in .NET 4.0, even though they are addressable if .NET 4.5+ is

    # installed (.NET 4.5 is an in-place upgrade).

    [System.Net.ServicePointManager]::SecurityProtocol = 3072 -bor 768 -bor 192 -bor 48

}

catch {

    Write-Output 'Unable to set PowerShell to use TLS 1.2 and TLS 1.1 due to old .NET Framework installed. If you see underlying connection closed or trust errors, you may need to upgrade to .NET Framework 4.5+ and PowerShell v3'

} 

That I put into the "build.ps1" file, right after line: Write-Host "Preparing to run build script..."