gtk2-engine-cleanice from openSUSE:Backports:SLE-15 project

需要 standard ，用 root 執行：

zypper addrepo https://download.opensuse.org/repositories/openSUSE:Backports:SLE-15/standard/openSUSE:Backports:SLE-15.repo
zypper refresh
zypper install gtk2-engine-cleanice