Run `apt-get update` before installing unix dependencies

[mike0sv]

In docker build, some unix dependencies will fail to install unless apt is updated first. We need to

1. if unix dependencies are present, run update before installing them
2. use best practices for it like doing updating and installation in one step, clear apt cache in the same step to make layer size smaller
3. add option to docker build context to be able to alter updating and clearing commands to support other base images