build-inside-vm.sh:
Change the source of /etc/resolv.conf to point to
/run/systemd/resolve/stub-resolv.conf, as it provides support for
per-interface resolving [1].
Fixes #123 (closed)
[1] https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html#/etc/resolv.conf