Remove all the repeated configuration and make gitlab configuration more
compact.
Tested: OK.

- Now all packages will build on two architectures, amd64 and i386

be it tar.xz or tar.gz

- disabled the passing of artifacts between stages

- Added the allow failure option, so as to enable completing of the full pipeline,
  even if the intermmediate jobs fail.

- changed the way artifacts are retrieved

- reduced the artifacts archiving time to 5 hours instead of 2 weeks.