Two distinct makefile directories are in use:
  - Common library makefiles (onf-make/)
  - Project specific makefile logic (local/)

Makefile logic is loaded/accessed through make macros:
    ONF_MAKEDIR=   Common makefile targets and logic
    MAKEDIR=       Repository/project specific targets

Common library targets are defined/augmented as double colon rules:
    build clean help sterile test :: # dup targets OK

    % make sterile test

All other targets are defined and accessed as single colon rules:
    repo-rule : # fail on duplicate targets


All makefiles/ logic can be access from the top level Makefile
==============================================================

TOP ?= $(strip $(dir $(abspath $(lastword $(MAKEFILE_LIST))) ) )    
include $(TOP)/config.mk
include $(TOP)/makefiles/include.mk

Which in turn will load onf-make/ and local/
============================================
include $(ONF_MAKE)/makefiles/include.mk
include $(MAKEDIR)/makefiles/include.mk

% make sterile build

# [EOF]