make help target cleanup

Makefile
makefiles/help/include.mk
makefiles/lint/include.mk
makefiles/lint/makefile.mk
makefiles/lint/.........mk
-------------------------
  o Implement topic help:: using 3 distinct targets.
  o help-summary - displays one-line topic help.
  o help-simple  - displays common topic help (lint, build, test)
  o help-verbose - exhaustive topic help for targets.
  o help (default) help-summary + help-simple (see {gerrit,lint}/help.mk)
  o Align all help text on string '[target]' from make cmd usage.
  o Restore JJB_VERSION ?= 2.8.0 in case of variant conflict with v4.1.0 in use.

makefiles/gerrit/help.mk
makefiles/gerrit/include.mk
---------------------------
  o Add gerrit command line convenience targets.
  o replication-status target shows health of gerrit-to-github mirror.

jjb/voltha-scale.yaml
---------------------
  o Lint cleanups, remove duplicate definitions.

Change-Id: I1c40fc0b5a61e3962e3481f0eae7266c5a6f2b2e
diff --git a/makefiles/consts.mk b/makefiles/consts.mk
index 4e3e24d..bac4362 100644
--- a/makefiles/consts.mk
+++ b/makefiles/consts.mk
@@ -30,8 +30,9 @@
 # [DEBUG] make {target} HIDE=
 HIDE        ?= @
 
-env-clean   = /usr/bin/env --ignore-environment
-xargs-n1    := xargs -0 -t -n1 --no-run-if-empty
+env-clean      ?= /usr/bin/env --ignore-environment
+xargs-n1       := xargs -0 -t -n1 --no-run-if-empty
+xargs-n1-clean := $(env-clean) $(xargs-n1)
 
 ## -----------------------------------------------------------------------
 ## Default shell:
@@ -44,6 +45,8 @@
 $(if $(have-shell-bash),$(null),\
   $(eval export SHELL := bash -euo pipefail))
 
+export SHELL ?= bash -euo pipefail
+
 $(if $(DEBUG),$(warning LEAVE))
 
 # [EOF]