Fully clean repository before start building

Signed-off-by: Marco Marinello <mmarinello@sezf.it>

.gitlab-ci.yml

@@ -17,6 +17,7 @@ rebuild-squashfs:
   script:
     - apt-get update -qy
     - apt-get install -y build-essential debhelper libncurses5-dev libglib2.0-dev libgeoip-dev libtokyocabinet-dev zlib1g-dev libncursesw5-dev libbz2-dev unzip wget squashfs-tools openssh-client
+    - make full-clean
     - make rebuild-squashfs
 
   # The files which are to be made available in GitLab