azure - Customising web.config when publishing a multi-tenant project to Azure

Question

I have a VS2012 solution that contains a multi-tenant MVC web project that I want to publish to multiple websites on a single Azure web role. I've changed my .csdef so that it contains multiple sites like so:

<Sites>
  <Site name="Web">
    <Bindings>
      <Binding name="Endpoint1" endpointName="Endpoint1" />
    </Bindings>
  </Site>
  <Site name="Web2" physicalDirectory="..\..\..\[source dir]">
    <Bindings>
      <Binding name="Endpoint1" endpointName="Endpoint1" hostHeader="secondsite.com" />
    </Bindings>
  </Site>
</Sites>

My question is: how can I deploy a different version of the Web.config to each site as part of the publication process in order to accommodate the different tenants?