The advantage of a real VM (qemu or virtualbox) is IMHO that isolation is bigger (you can really move the VMs around if/as needed), and you get the networking for free (as long as you use NAT which is perfectly fine for this use-case).

With lxc (and docker) the main disadvantage I see is the networking, as you need (yourself) to set-up a bridge interface. This is easy, but each distro does it differently (ifupdown, systemd-networkd, network manager, whatever).

And this is only about plain-old scratchbox sdk. Meaning it doesn't even need a graphical interface. You can run it with qemu in the background and ssh into it whenever you feel like doing something.

If/when QtSDK is added to this then you need X, and AFAIK running X on LXC (or docker) is not a trivial thing.

Anyway, with the clean image (now in a vmdk container) I can extract this and make a rootfs suitable for LXC, docker, or even for unpacking onto real hardware. Of course you still need a kernel (and possibly an initramfs), but that's not an issue.

Anyway, I'd be happy if (in a few hours) some of you can download the Virtualbox image I'm uploading. Virtualbox can easily do snapshots, so make sure you use them.