scripts/build_utils.sh: add lang=none option to sources.list

scripts/build_utils.sh: add lang=none option to sources.list

some mirrors do not contains the package description translations. when
apt tries to download the packages descriptions, it fails like:

E: Failed to fetch
http://mirror.yandex.ru/mirrors/launchpad/ubuntu-toolchain-r/dists/xenial/main/i18n/Translation-en
404  Not Found [IP: 213.180.204.183 80]
E: Some index files failed to download. They have been ignored, or old
ones used instead.

for more info, see sources.list(5) and apt.conf(5). the default value
of "lang" is set by Acquire::Languages, which is in turn "en" and
"environment" by default. we need to override them with "none".

Fixes #1136
Signed-off-by: Kefu Chai <kchai@redhat.com>