Adding rpm-build to the Dockerfile (#117)

rpmbuild in the DTK helps when having to rebuild source kernel module RPMs
to match the RHCOS kernel version

Co-authored-by: Jason Kincl <jkincl@redhat.com>

Author: openshift-cherrypick-robot

Dockerfile

@@ -42,7 +42,7 @@ RUN yum -y install xz diffutils flex bison \
     && yum clean all
 
 # Packages needed to build driver-containers
-RUN yum -y install git make \
+RUN yum -y install git make rpm-build \
     && yum clean all
 
 # Packages needed to sign and run externally build kernel modules