https://wiki.centos.org/HowTos/SetupRpmBuildEnvironment
The qemu tarball is too big for github, so download separately:
cd ~/rpmbuild/SRPMS
dnf download --source qemu-kvm
cd ~/rpmbuild/SOURCES
rpm2cpio ~/rpmbuild/SRPMS/qemu-kvm-6.2.0-35.module_el8+466+00f6f2b0.src.rpm | cpio -idmv
Build the RPMs:
cd ~/rpmbuild/SPECS
yum-builddep qemu-kvm.spec
rpmbuild -ba qemu-kvm.spec