Support building Onionspray without sudo privileges on Debian-like systems

Description

Onionspray build scripts relies on sudo to install system-wide packages. This could be avoided if the scripts could check first whether the needed packages are installed.

Useful for installation procedures such as those using the Onionspray Ansible Role which can install dependencies by themselves (related to tpo/onion-services/ansible/onionspray-role#2).

Task

• Update the build scripts so they first check for installed packages before attempting to install missing ones using `sudo. Focus at least on Debian and Ubuntu.

Time estimation

• Complexity: very small (0.5 day)
• Uncertainty: low (x1.1)
• Reference (adapted)