ISO: Use --joliet-long names.

ISO: Use --joliet-long names.

Armband adds similar files, which tend to have long names and only
differ in suffixes (e.g. DEBs for amd64 vs arm64).

This works around ISO build error(s) like:

"genisoimage: Error:
./ubuntu/pool/main/g/golang-gogoprotobuf/golang-gogoprotobuf\
-dev_0.0~git20150828.0.6cab0cc-1~u14.04+mos1_amd64.deb and
./ubuntu/pool/main/g/golang-gogoprotobuf/golang-gogoprotobuf\
-dev_0.0~git20150828.0.6cab0cc-1~u14.04+mos1_arm64.deb
have the same Joliet name"

Change-Id: I89d9816d86176d80bcc76f5f90c8391b0664ab82
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>