makefile: add a comment to defaults.py handling

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -160,6 +160,8 @@ export UTILS_DIR     ?= $(FLOW_HOME)/util
 export SCRIPTS_DIR   ?= $(FLOW_HOME)/scripts
 export TEST_DIR      ?= $(FLOW_HOME)/test
 
+# __SPACE__ is a workaround for whitespace hell in "foreach"; there
+# is no way to escape space in defaults.py and get "foreach" to work.
 $(foreach line,$(shell $(SCRIPTS_DIR)/defaults.py),$(eval export $(subst __SPACE__, ,$(line))))
 
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