tools: Provide multicall lxc binary

tools: Provide multicall lxc binary

Create a binary, which embeds all lxc tools similar way as busybox
embeds its applets. This is handy for embedded systems as it saves
roughly 90% of the disk space.

To disable normal tools and use multicall binary exclusively use the
following meson setup options:
  -Dtools=false -Dtools-multicall=true

Signed-off-by: Petr Malat <oss@malat.biz>