Update .gitlab-ci.yml - adding debootstrap to the installation

1 job from master in 4 minutes 9 seconds (queued for 7 seconds)
Status Job ID Name Coverage
  Buildiso
failed #11
run-build

04:09

 
Name Stage Failure
failed
run-build Buildiso There is an unknown failure, please try again
Universal Time is now:  Mon Oct 30 09:25:42 UTC 2017.
Run 'dpkg-reconfigure tzdata' if you wish to change it.

$ apt-get install -y build-essential devscripts binutil debootstrap git
Reading package lists...
Building dependency tree...
Reading state information...
E: Unable to locate package binutil
ERROR: Job failed: exit code 1