Automatic `apt-get -y install` should use `--no-upgrade`

[afcady]

When apt-get -y install is used by automated installers, they should use --no-upgrade. Users probably aren't expecting to have their systems upgraded by this build script, and it is unlikely ever to be needed.

(Even if it were needed to get a specific version, the current approach would be inadequate, since users might not have the updated apt sources. The correct approach would be generating a package with dependencies with version bounds, then installing that.)