For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:huakim:matrix/openSUSE_Tumbleweed/home:huakim:matrix.repo
zypper refresh
zypper install rpm-build
For openSUSE Factory PowerPC run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:huakim:matrix/openSUSE_Factory_PowerPC/home:huakim:matrix.repo
zypper refresh
zypper install rpm-build
For openSUSE Factory LegacyX86 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:huakim:matrix/openSUSE_Factory_LegacyX86/home:huakim:matrix.repo
zypper refresh
zypper install rpm-build
For openSUSE Factory ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:huakim:matrix/openSUSE_Factory_ARM/home:huakim:matrix.repo
zypper refresh
zypper install rpm-build