ci: add hip4.2 base image

.gitlab/ci/docker/hip4.2/Dockerfile

+FROM rocm/dev-ubuntu-20.04:4.2
+MAINTAINER Brad King <brad.king@kitware.com>
+
+ENV PATH="/opt/rocm/bin:$PATH"
+
+COPY install_deps.sh /root/install_deps.sh
+RUN sh /root/install_deps.sh

.gitlab/ci/docker/hip4.2/install_deps.sh

+#!/bin/sh
+
+set -e
+
+apt-get update
+
+# Install development tools.
+apt-get install -y --no-install-recommends \
+    g++ \
+    curl \
+    git
+
+apt-get clean