Add install -y to allow unattended install without a pipe

[bonachea]

The install.sh script currently defaults to requiring interactive input to install dependencies, which is unfriendly in automated/scripted contexts.

The --help output advises:

For a non-interactive build with the 'yes' utility installed, execute
yes | ./install.sh <other_options>

This is a reasonable workaround on the command line (and apparently sufficient for GitHub CI). However can be awkward to incorporate into other automated packaging scenarios that are less flexible. Also from a design perspective it's ugly to recommend a piped input to force a behavior necessary to accommodate an important use case that would be better to support directly in the script.

This issue requests a install.sh -y option so unattended installs don't need a pipe, eg:

./install.sh -y <other_options>