Fix identity package filtering

Fix identity package filtering

We only want to filter out identity package builds on
official builds that aren't windows x64, to avoid building
and publishing them more then once in an official build.

We also need to account for source-build which sets the
OfficialBuildId property to replicate the official builds,
so we also look at the DotNetBuildOffline property to
determine that we should still build the identity package.