How can I deploy a SharePoint 2013 Reusable Workflow in the Host Web without SP Designer

Hi,

We are developing an app that requires a Workflow in the HostWeb.
I have successfully tested using a Reusable Workflow in my Dev environment using SharePoint designer, but have not found a supported method of deploying this to Office 365 without SP Designer.

What is the recommended way of deploying a Reusable Workflow as part of my App's deployment?
I do not want to use SP Designer if possible....

Thanks in advance.

Alex