Normalize MAKEDIR, ONF_MAKEDIR and ONF_MAKE

Change-Id: I3908c0738dbbed180d62dc0f4ba656226035ba5a
diff --git a/makefiles/lint/shell.mk b/makefiles/lint/shell.mk
index 704038c..a02da31 100644
--- a/makefiles/lint/shell.mk
+++ b/makefiles/lint/shell.mk
@@ -34,7 +34,7 @@
 shell-check      := shellcheck
 
 shell-check-args += --check-sourced
-shell-check-args += --external-sources
+shell-check-args += --extenal-sources
 
 ##-------------------##
 ##---]  TARGETS  [---##