I have a snap which is very large and failed to build due to running out of memory in multipass. I set SNAPCRAFT_BUILD_ENVIRONMENT_MEMORY=8G and re-ran snapcraft. It re-used the previous VM rather than noting the change in RAM, to take the opportunity to launch a new one. Perhaps snapcraft could detect the change in resources and act accordingly, cleaning or at least suggesting a clean is worthwhile if the environment around multipass changes?