VOL-4846 - Added targets lint-chart & lint-helm

README.md
Makefile
makefiles/lint/helm.mk
makefiles/lint/include.mk
=========================
   * In the quest to stop having jenkins failing jobs post checkin for
     content problems added targets lint-chart & lint-helm which invoke
     commands mentioned in README.md.
   * Logic is currently conditional: make lint-helm UNSTABLE=1, failures
     will need to be cleaned up before the command can be run as a default.

Change-Id: I6b445a6600c283b8068201a006792aeacf5407aa
diff --git a/makefiles/variables.mk b/makefiles/variables.mk
new file mode 100644
index 0000000..72d449b
--- /dev/null
+++ b/makefiles/variables.mk
@@ -0,0 +1,26 @@
+# -*- makefile -*-
+# -----------------------------------------------------------------------
+# Copyright 2022 Open Networking Foundation (ONF) and the ONF Contributors
+#
+# 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.
+#
+# SPDX-FileCopyrightText: 2022 Open Networking Foundation (ONF) and the ONF Contributors
+# SPDX-License-Identifier: Apache-2.0
+# -----------------------------------------------------------------------
+
+help ::
+	@echo
+	@echo "[VARIABLES]"
+	@echo "  UNSTABLE=                     Build targets prone to failure (lint-helm)"
+
+# [EOF]