Add Dockerfile.rhel8

A separate file is required, as the changes necessary for building with
RHEL 8 content are not compatible with RHEL 7.

Dockerfile.rhel8

@@ -0,0 +1,43 @@
+FROM registry.svc.ci.openshift.org/ocp/builder:golang-1.14 AS builder
+WORKDIR /go/src/github.com/openshift/cluster-node-tuning-operator
+COPY . .
+RUN make build
+
+FROM registry.svc.ci.openshift.org/ocp/4.6:base AS tuned
+WORKDIR /root
+COPY assets/tuned /root
+RUN INSTALL_PKGS=" \
+      git rpm-build make desktop-file-utils patch \
+      python3 python3-configobj python3-pyudev \
+      " && \
+    yum install --setopt=tsflags=nodocs -y $INSTALL_PKGS && \
+    cd daemon && \
+    LC_COLLATE=C cat ../patches/*.diff | patch -Np1 && \
+    make rpm PYTHON=/usr/bin/python3 && \
+    rm -rf /root/rpmbuild/RPMS/noarch/{tuned-gtk*,tuned-utils*,tuned-profiles-compat*,tuned-profiles-nfv*}
+
+FROM registry.svc.ci.openshift.org/ocp/4.6:base
+COPY --from=builder /go/src/github.com/openshift/cluster-node-tuning-operator/_output/cluster-node-tuning-operator /usr/bin/
+COPY manifests /manifests
+ENV APP_ROOT=/var/lib/tuned
+ENV PATH=${APP_ROOT}/bin:${PATH}
+ENV HOME=${APP_ROOT}
+WORKDIR ${APP_ROOT}
+COPY --from=builder /go/src/github.com/openshift/cluster-node-tuning-operator/_output/openshift-tuned /usr/bin/
+COPY --from=builder /go/src/github.com/openshift/cluster-node-tuning-operator/assets ${APP_ROOT}
+COPY --from=tuned   /root/rpmbuild/RPMS/noarch /root/rpms
+RUN INSTALL_PKGS=" \
+     hdparm kernel-tools tuna socat \
+      " && \
+    mkdir -p /etc/grub.d/ /boot && \
+    yum install --setopt=tsflags=nodocs -y $INSTALL_PKGS && \
+    rpm -V $INSTALL_PKGS && \
+    yum --setopt=tsflags=nodocs -y install /root/rpms/*.rpm && \
+    touch /etc/sysctl.conf && \
+    yum clean all && \
+    rm -rf /var/cache/yum ~/patches /root/rpms && \
+    useradd -r -u 499 cluster-node-tuning-operator
+ENTRYPOINT ["/usr/bin/cluster-node-tuning-operator"]
+LABEL io.k8s.display-name="OpenShift cluster-node-tuning-operator" \
+      io.k8s.description="This is a component of OpenShift and manages the lifecycle of node-level tuning." \
+      io.openshift.release.operator=true