Integrate gitlab-ci/lpag/add_rpi_qemu
[RASPBERRY] Add support to Raspberry Pi 4 machine
- The Raspberry Pi 4 machine only supports U-Boot in Edgehog Things distro, for this reason we introduce a check on the presence of U-Boot files and eventually not deploy the package in case no files are found.
- At build time, we only check the number of U-Boot artifacts and give a warning if they are less than expected.