Don't reference target-specific variable from dependency list

Apprently target-specific variables are only valid for the body of
the target, not its dependency list, so the dependency on the zip file
wasn't being added.

Bug: 340392832
Test: m, rm file_list.txt and the zip file, m again, and ensure we don't get an error that the zip file doesn't exist
Change-Id: Idaca6606ff24055aa98c78ca1206b587cc1df4d2