main.mk: escalate the comment to a warning

The problem manifests itself when the naive parser ignores
any conditions that might have been set in the makefiles
included with subsequent attempt to run a target which has
its actual rule defined within e.g. "ifdef DEBUG" clause
(as is the case for conf.d/test.mk); that will fail with
no proper diagnostics currently.

Maybe this would be of some use (but then again maybe not):
http://stackoverflow.com/questions/3063507/list-goals-targets-in-gnu-make

main.mk

@@ -34,7 +34,8 @@ include $(sort $(wildcard lib/*.mk))
 include conf.d/*.mk
 include features.in/*/config.mk
 
-# starts to look copypastey
+# FIXME: this is buggy since *.mk can expose parts conditionally
+#        (e.g. test.mk does DEBUG-only bits) and these will fail
 DISTRO_TARGETS := $(shell sed -n 's,^\(distro/[^:.]\+\):.*$$,\1,p' \
 		lib/distro.mk $(wildcard conf.d/*.mk) | sort -u)
 VE_TARGETS := $(shell sed -n 's,^\(ve/[^:.]\+\):.*$$,\1,p' \