package-infra: comment why all checks are done in pkg-generic

[Thomas: fix duplicate -> duplicating.]

Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/pkg-generic.mk

@@ -702,7 +702,11 @@ $$(foreach pkg,$$($(2)_PROVIDES),\
 	$$(eval $$(call virt-provides-single,$$(pkg),$$(call UPPERCASE,$$(pkg)),$(1))$$(sep)))
 endif
 
-# Ensure unified variable name conventions between all packages
+# Ensure unified variable name conventions between all packages Some
+# of the variables are used by more than one infrastructure; so,
+# rather than duplicating the checks in each infrastructure, we check
+# all variables here in pkg-generic, even though pkg-generic should
+# have no knowledge of infra-specific variables.
 $(eval $(call check-deprecated-variable,$(2)_MAKE_OPT,$(2)_MAKE_OPTS))
 $(eval $(call check-deprecated-variable,$(2)_INSTALL_OPT,$(2)_INSTALL_OPTS))
 $(eval $(call check-deprecated-variable,$(2)_INSTALL_TARGET_OPT,$(2)_INSTALL_TARGET_OPTS))