centos-release-gluster-legacy removes unmaintained versions of
centos-release-gluster* packages from the system..
This package needs to get build by the CentOS core team that maintains the Extras repository.
Building the package can be done like this:
$ rpmbuild -bs \
--define "_sourcedir $PWD/SOURCES" --define "_srcrpmdir $PWD" \
--define "dist .el7.centos" \
SPECS/centos-release-gluster-legacy.spec
$ cbs build --scratch \
storage7-gluster-9-el7 \
centos-release-gluster-legacy-8-1.el7.centos.src.rpm