Copy system version of the api-versions.xml file to dist

Copies the system version of the `api-versions.xml` file to a file
`api-versions_system.xml` in the top level dist directory.

Bug: 190665366
Test: m sdk dist
      # Check to make sure that the file exists.
Change-Id: Ie139f81a819eb5f389363ffdefa7bc42d36804e0