gitlab-ci: Build debs

Override upstream CI to build Debian packages
4 jobs for pureos/sloppy in 6 minutes and 53 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Package
passed #273404
librem5
package:deb-debian-buster

00:02:05

passed #273405
librem5:arm64
package:deb-debian-buster:arm64

00:05:13

 
  Test Package
passed #273406
librem5
autopkgtest-debian-buster-package

00:01:15

passed #273407
librem5
lintian-debian-buster-package

00:00:40