class library dll’s not added / installed / referenced / moved to assembly GAC while deployment of package automatically in SharePoint SP 2010 / 2007

To install classlibrary dll to GAC automatically during the deployment of WSP package of Sharepoint SP 2007 / 2010, refer the following instruction steps,

1. Open the Package designer in the SharePoint project.
2. Select the Advanced tab.
3. Click the Add button.
4. Select the Add Assembly from Project Output menu item.
5. Use the Source Project dropdown to select which project in your solution should have its assembly included.
6. Make sure the Deployment Target is set to GlobalAssemblyCache.
7. Click OK.
8. Repackage and redeploy the SharePoint project. 

The WSP package should now contain the class library's assembly and the WSP's package manifest should have been updated according.,

For more details, please refer : 

http://msdn.microsoft.com/en-us/library/ee231595%28VS.100%29.aspx