For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:khnazile:video/openSUSE_Leap_15.2/home:khnazile:video.repo
zypper refresh
zypper install ninja
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:khnazile:video/openSUSE_Leap_15.1/home:khnazile:video.repo
zypper refresh
zypper install ninja
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:khnazile:video/openSUSE_Leap_15.0/home:khnazile:video.repo
zypper refresh
zypper install ninja