how to use this dragonboard-builder tool to create fastboot images instead of sdcard image.
regards,
vinaysimha
Syntax is identical to ubuntu image, only difference is in produced images, being ready for fastboot
However before you proceed:
at the moment you will need to use edge channel, as gadget snap supporting this way of building is only in edge channel, and there is open issue with auto resizing at first boot @ogra can keep you updated about this
For now, just manually resize once booted, just be fast before device runs out of space 
$ sudo dragonboard-builder.build-db410c-image -c edge --extra-snaps ubuntu-xenial/dragonboard-kernel_4.4.0-1103.108_arm64.snap --extra-snaps dragonboard-gadget/dragonboard_16.04-0.18_arm64.snap 63b0.model
Unknown parameter ‘–extra-snaps’
Builder for UbuntuCore for dragonboard
please suggest