libvirt-client from home:olh:xen-4.21 project

需要 SLE 15 ，用 root 執行：

zypper addrepo https://download.opensuse.org/repositories/home:olh:xen-4.21/SLE_15/home:olh:xen-4.21.repo
zypper refresh
zypper install libvirt-client