When I launch the "koji" comand, build fails because it does not find g++
(see : https://kojipkgs.fedoraproject.org//work/tasks/9140/66659140/build.log )
However, I put gcc-c++ in the BuildRequires line
(see : https://github.com/grosjo/fts-xapian/blob/master/PACKAGES/RPM/fts-xapian.spec )