Avoid docker warning: - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>
Update instructions and CI for cross-compilation on Ubuntu 22. Note that for the dockerfile, we use egrep -L which has changed and does not exit with code 0 on no match. Instead, use -vqz to invert return code (0 if nothing found, otherwise 1).