AFAIK, there is no option in Group Policy to create or enforce the creation of a computer account in case it does not exist.
The policy you may think about is the following:
Computer Configuration / Windows Settings / Security Settings / Local Policies / User Rights Assignment / Add workstations to domain
This policy will define who is able to add computers to the domain. The process of creating the computer account is not a GPO setting.
What you can do is using a PS script like DSPatrick mentioned to create computers objects in the correct OU before the computer will join the domain. This is probably the best option in case you don't want to delegate permission on a specific OU.
hth