mk_payload is a binary used by ARCVM to create a composite disk of using apexes. See go/arcvm-block-apex for more background.

To update the mk_payload binary used by CrOS builders, do the following

To update to a newer version of mk_payload, you'll need to

• Download push_to_device.zip from an Android builder (e.g ab/git_master-arc-dev). Make sure to include the version # nocheck used here in your commit.
  • If you want to build this manually, you can run m mk_payload from your lunch'd Android checkout. However, you should only upload a binary from a builder.
• Unzip it
  • unzip -d ptd push_to_device.zip
• run the files/gather.sh script
  • files/gather.sh ptd/bin/mk_payload <NEW_VERSION>
• rename the ebuild, incrementing the version
  • e.g. if incrementing from 0.0.3 -> 0.0.4, you would do git mv mk-payload-0.0.3.ebuild mk-payload-0.0.4.ebuild
• cros_sdk
• (inside chroot) sudo ebuild <PATH_TO_THIS_EBUILD> manifest

The only place this is used is inside board_specific_setup, so to test locally you'll have to manually create a new image with it.