JSON for Raspberry Pi OS

[Psychesnet]

Hi, I would like to pack custom raspberry pi os for pi4, but I don't see the json for pi os at boards/raspberry-pi-4. Do you have any suggestions to have that json?
I try to use the json from old version(1.6.6) packer, looks like the key item at json is quite different. Need your help. Thanks.

[rvoitenko]

@Psychesnet I've used as template boards/rapberry-pi/raspios-lite-arm.json, and image from https://downloads.raspberrypi.org/ and added the following to make unpack works for xz archives:

      "file_unarchive_cmd": [
        "xz",
        "-d",
        "$ARCHIVE_PATH"
      ],

works like a charm