python-pyelftools is not packaged for RHEL/CentOS with the exception of RHEL7 EPEL. Add command to install it with pip. Fixes: f0f93a7adfee ("buildtools: use Python pmdinfogen") Signed-off-by: Kevin Traynor <ktraynor@redhat.com> Acked-by: Bruce Richardson <bruce.richardson@intel.com>