Find how to 'apt-get update' of a specific debian package

[hyunsik-yoon]

If backend is provided from a debian repo, let's update apt cache only for a specific debian repo.

from #569 (comment)

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If the artifactory data is changed when user requests toolchain lists, how can we control this situation?

Maybe we can have setInterval() that keeps calling apt-get update one or twice per day while ONE-vscode is up and running.
However, some users may not call apt-get update so we may need to find out some way to call apt-get update for backend Debian repo.

[hyunsik-yoon]

The following command may work:

sudo apt-get update -o Dir::Etc::sourcelist=${SOURCELIST}" \
    -o Dir::Etc::sourceparts="-" -o APT::Get::List-Cleanup="0"

[hyunsik-yoon]

If a package needs latest version of other package (which should be updated with apt-get update), this command may fail.
Let's use apt-get update for now.