refactor build scripts

[renner0e]

so we are doing this in our Containerfile, should speed up local builds tremendously.

RUN --mount=type=bind,from=ctx,source=/,target=/ctx \
    --mount=type=cache,dst=/var/cache \
    --mount=type=cache,dst=/var/log \
    --mount=type=tmpfs,dst=/tmp \
    /ctx/01-packages.sh

RUN --mount=type=bind,from=ctx,source=/,target=/ctx \
    --mount=type=cache,dst=/var/cache \
    --mount=type=cache,dst=/var/log \
    --mount=type=tmpfs,dst=/tmp \
    /ctx/02-firmware.sh

Currently we make one tiny change in something that doesn't matter at all and we rebuild the whole as there is 0 caching

We might also want to make it look like bluefin-lts ublue-os/bluefin#3552