Update to v2021pre, new apertis-flatdeb-builder and fix upload process

The new apertis-flatdeb-builder already embedded requested packages and the apertis-flatdeb program.
Move runtime, SDK and curl app to v2021pre.
The suite recipe name should be in sync with the Apertis version.

Split the creation of base, platform and sdk runtime as process fails to access to network on 2nd call to debos, with the following errors:

Error: Os { code: 98, kind: AddrInUse, message: "Address already in use" }
Core dump limits :
	soft - NONE
	hard - NONE
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...OK
Checking advanced syscall emulation patch for ptrace...OK
Checking environment variables for a tempdir.../scratch
Checking if /scratch is on tmpfs...OK
Checking PROT_EXEC mmap in /scratch...OK
Adding 3395584 bytes to physical memory to account for exec-shield gap
Event loop failed: Connection timed out
…
2020/09/09 07:04:39 apt-install | E: Failed to fetch https://repositories.apertis.org/apertis/pool/hmi/m/mildenhall/mildenhall_0.2020.1bv2021dev1b1_all.deb  Temporary failure resolving 'repositories.apertis.org'
2020/09/09 07:04:39 apt-install | E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
2020/09/09 07:04:39 apt-install | Container root failed with error code 100.
2020/09/09 07:04:39 apt-install |
2020/09/09 07:04:39 apt-install | ERROR:flatdeb.apt-install:Command '['systemd-nspawn', '--directory=/scratch/root', '--as-pid2', '--tmpfs=/run/lock', '--register=no', 'env', 'DEBIAN_FRONTEND=noninteractive', 'apt-get', '-y', '--no-install-recommends', 'install', 'libc6:amd64', 'libstdc++6:amd64', 'libsystemd0', 'mildenhall']' returned non-zero exit status 100.
2020/09/09 07:04:39 Action `run` failed at stage Run, error: exit status 1

Signed-off-by: Frédéric Danis frederic.danis@collabora.com