repro steps:
install flutter sdk locally on machine and run the calc/example, flutter uses junction/symlinks during I believe snapcraft can't handle them well.
snapcraft stage source --use-lxd --verbosity debug snapcraft stage websocket --use-lxd --verbosity debug snapcraft stage packages --use-lxd --verbosity debug snapcraft stage liquid terminal --use-lxd --verbosity debug
cd packages/calc/example flutter build linux snapcraft stage liquid terminal --use-lxd --verbosity debug