Support custom sysroot i.e. with custom additional libraries

[me21]

Please support custom sysroot. For example, mount actual Pi root over sshfs, or copy it locally using rsync. There can be additional libraries installed (i.e. WiringPi etc.).

[me21]

Oh, I've realized it's possible to modify utils/prepare-sysroot-full.sh. Still, mounting Pi root over sshfs has the benefit it doesn't take up local space. It might prove useful to somebody.

[GuillaumeLazar]

Nice idea!

The script could be updated to offer the option to choose between:

• the default sysroot
• a custom sysroot.

So everybody can use it in both way without modifying the script. What do you think about it?

[totolito]

I also vote for this option! ;-)