Always package NOTICE.xml.gz

To remove the reliance on UseSoongSystemImage. We can always package
it, but not install it, so that it appears for soong built filesystems
but doesn't conflict with the make built version.

Test: m out/soong/.intermediates/build/make/target/product/generic/generic_system_image/android_common/fileList, verified that NOTICE.xml.gz was still there
Change-Id: I76d97a380b8c295f6d1cd8ea1c809229867ab890