Add ability to disable build of all targets Allow passing of '--target-list=' to configure to request that all targets are to be disabled. This allows for doing a very fast tools-only build of things like qemu-img, qemu-io, qemu-nbd. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>