Separate dockerfiles for more efficient build

Change-Id: I526f4317ada36d1ac24d904d3ffb873611c0225c
diff --git a/Dockerfile.enb b/Dockerfile.enb
new file mode 100644
index 0000000..dc3503e
--- /dev/null
+++ b/Dockerfile.enb
@@ -0,0 +1,53 @@
+#
+# Copyright 2019-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
+#
+# 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.
+
+ARG build_base
+
+FROM $build_base AS enb-builder
+WORKDIR /openairinterface5g
+ENV USER=root
+RUN /bin/bash -c "source oaienv" && cd cmake_targets && ./build_oai --eNB -t ETHERNET -c
+
+FROM ubuntu:16.04 AS lte-softmodem
+RUN apt-get update && apt-get install -y \
+    libssl1.0.0 \
+    libnettle6 \
+    libsctp1 \
+    libforms2 \
+    libprotobuf-c1 \
+    libyaml-0-2 \
+    libconfig9 \
+    dnsutils \
+    iproute2 \
+    iputils-ping \
+ && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /openairinterface5g/cmake_targets
+COPY --from=enb-builder /openairinterface5g/cmake_targets/ .
+
+# Label image
+ARG org_label_schema_version=unknown
+ARG org_label_schema_vcs_url=unknown
+ARG org_label_schema_vcs_ref=unknown
+ARG org_label_schema_build_date=unknown
+ARG org_opencord_vcs_commit_date=unknown
+
+LABEL org.label-schema.schema-version=1.0 \
+      org.label-schema.name=lte-softmodem \
+      org.label-schema.version=$org_label_schema_version \
+      org.label-schema.vcs-url=$org_label_schema_vcs_url \
+      org.label-schema.vcs-ref=$org_label_schema_vcs_ref \
+      org.label-schema.build-date=$org_label_schema_build_date \
+      org.opencord.vcs-commit-date=$org_opencord_vcs_commit_date