Add rules to generate CTS coverage report for System APIs

Bug: 136021260
Test: 1. Run 'make cts-system-api-test-coverage' and verify the html report is
         generated.
      2. Run 'make cts-system-api-xml-test-coverage' and verify the xml report
         is generated.

Change-Id: If96fd03df9a078a83384670d45fe5ed414319c22
1 file changed