Add unit test docker file

ci-scripts/docker/Dockerfile.unittest.ubuntu20

+#/*
+# * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
+# * contributor license agreements.  See the NOTICE file distributed with
+# * this work for additional information regarding copyright ownership.
+# * The OpenAirInterface Software Alliance licenses this file to You under
+# * the OAI Public License, Version 1.1  (the "License"); you may not use this file
+# * except in compliance with the License.
+# * You may obtain a copy of the License at
+# *
+# *      http://www.openairinterface.org/?page_id=698
+# *
+# * Unless required by applicable law or agreed to in writing, software
+# * distributed under the License is distributed on an "AS IS" BASIS,
+# * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# * See the License for the specific language governing permissions and
+# * limitations under the License.
+# *-------------------------------------------------------------------------------
+# * For more information about the OpenAirInterface (OAI) Software Alliance:
+# *      contact@openairinterface.org
+# */
+#---------------------------------------------------------------------
+#
+# Dockerfile for the Open-Air-Interface BUILD service
+#   Valid for Ubuntu 20.04
+#
+#---------------------------------------------------------------------
+
+FROM ran-base:develop as ran-tests
+
+RUN rm -Rf /oai-ran
+WORKDIR /oai-ran
+COPY . .
+
+WORKDIR /oai-ran/build
+RUN cmake -GNinja -DENABLE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug .. && ninja tests