llvm20 from X11:XOrg project

对于 openSUSE Leap 15.6，请以根用户 root 运行下面命令：

zypper addrepo https://download.opensuse.org/repositories/X11:XOrg/openSUSE_Leap_15.6/X11:XOrg.repo
zypper refresh
zypper install llvm20