gstreamer-devtools from home:alveus:plexmedia project

需要 openSUSE Tumbleweed ，用 root 執行：

zypper addrepo https://download.opensuse.org/repositories/home:alveus:plexmedia/openSUSE_Tumbleweed/home:alveus:plexmedia.repo
zypper refresh
zypper install gstreamer-devtools