releasetools: Allow creating target_files with ZIP64.

add_img_to_target_files.py fails when the target_files.zip is over 4GiB
when adding IMAGES/ folder. Specify the flag to allow creating
target_files.zip with ZIP64 extension.

Other zip artifacts (-img.zip, -ota.zip etc) remain in non-ZIP64 format.
zip2zip is not affected, which still creates non-ZIP64 zips even when
copying from target_files in ZIP64.

Bug: 30961841
Test: "make dist" with large system image and check the artifacts.

Change-Id: I0568745f01ef8f0239081f783eac92288d4fdd84