[VOL-5010] - Clone unit tests to run on a v2.12 branch

makefiles/consts.mk
makefiles/virtualenv.mk
-----------------------
  o Copy in latest library makefiles from repo:onf-make

global-jjb
packer/common-packer
--------------------
  o Upgrade LinuxFoundation submodules to the latest version.
  o global-jjb           : from=0.53.3 to=0.86.7
  o packaer/common-packer: from=0.1.0~22 to=0.12.1

.gitignore
makefiles/include.mk
makefiles/git/
makefiles/jjb/
--------------
  o Added convenience make targets to view submodule versions.
  o JJB target:jjb-gen added to prototype local pipeline edits.
  o Logic is conditional, library will only load when targets are requested.

jjb/voltha-test/voltha-certification/
jjb/voltha-test/voltha-certification/README
jjb/voltha-test/voltha-certification/master.yaml
------------------------------------------------
  o Create pseudo-branches within voltha testing so we can
  o 'branch' (simple directory copy) at release time VS
  o having to find and clone individual test suites from last release.

Change-Id: I3e0096d3326e76b3faa896d73183f9d28e946d06
diff --git a/makefiles/git/required.mk b/makefiles/git/required.mk
new file mode 100644
index 0000000..29fba88
--- /dev/null
+++ b/makefiles/git/required.mk
@@ -0,0 +1,32 @@
+# -*- makefile -*-
+# -----------------------------------------------------------------------
+# Copyright 2022-2023 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.
+# -----------------------------------------------------------------------
+# Intent: Conditionally load when named targets are requested.
+#   var ?= $(error ...) definitions are fatal to "make help" and others
+# -----------------------------------------------------------------------
+
+git-mk-targets := $(NULL)
+git-mk-targets := show-submodules
+
+# -----------------------------------------------------------------------
+# Define a flag to only load release targets when mentioned by name
+# Makefile can also explicitly define the flag to force always loading.
+# -----------------------------------------------------------------------
+$(foreach tgt,$(git-mk-targets),\
+  $(if $(findstring $(tgt),$(MAKECMDGOALS)),$(eval USE_ONF_GIT_MK := true))\
+)
+
+# [EOF]