CI: do the rebuilds via kaniko.

1 job for ci-changes in 14 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
failed #241221
build

00:00:14

 
Name Stage Failure
failed
build Build
++ echo 'Changed images: '\'' dav1d-debian-unstable'\'''
++ for d in $DIRS
++ '[' -d dav1d-debian-unstable ']'
Changed images: ' dav1d-debian-unstable'
+++ date +%Y%m%d%H%M%S
++ DATE=20181206205133
++ /kaniko/executor --no-push --context dav1d-debian-unstable --dockerfile /builds/videolan/docker-images-aarch64/Dockerfile --destination dav1d-debian-unstable-aarch64:20181206205133
/bin/bash: line 83: /kaniko/executor: cannot execute binary file: Exec format error
ERROR: Job failed: exit code 1