The tool currently generates a XML file with the root element only and its content will be filled in in following CLs.
Also disable the generation of NOTICE.xml.gz in make when USE_SOONG_DEFINED_SYSTEM_IMAGE is true, so the Soong module could be used without conflict.
Bug: 330949782
Bug: 338342381
Test: lunch aosp_cf_x86_64_phone-trunk_staging-eng && m, and check that system/etc/NOTICE.xml.gz have all the XML elements.
Test: lunch aosp_cf_x86_64_phone_soong_system-trunk_staging-eng && m, and check that system/etc/NOTICE.xml.gz has root element only.
Change-Id: I82e90bd9aa3dabc605acfe8da697ab1f7e7ecf9b
