I have my project in an SVN repository and it pulls in another SVN repository as an external. This works fine locally, but the external repository is not being synced in the cloud builds. So, naturally the builds fail.
Is there a specific setup or change I need to make so that SVN externals work?
SVN external might work in some cases but is not officially supported right now. In any case, you should make sure the base repository and the external one have the same credentials and use the same url format. Other than that, if it’s very important for you, please file a feature request! 
Hi David,
Thank you for getting back to me. I will file the feature request.
Can you give any additional information on the cases that might work? I’m happy to change my setup around. The two repositories do have the same credentials and are hosted by the same provider with the same settings.
Do you know if there s anything else I can do to make it more compatiable?
For anyone else interested you can vote here:
http://feedback.unity3d.com/suggestions/add-support-for-svn-externals
Best Regards,
Todd
No I have not built successfully with SVN externals myself, but I have to admin, I do not really have a good usecase either, but there are other customers who already used it properly in the past. I saw you already found one of them here. So maybe he can share his experience with you!