Normalize the product makefile path in inherit-product.

Some vendor product makefiles call $(inherit-product) on the same
product makefile with different paths, by using "../" in relative paths.
However inherit-product requires unique path as ID for a product
makefile, for bookkeeping purpose.
Normalize the product makefile path in inherit-product, if the path
contains "../".

Change-Id: I1a864ce120c713d8e79ec179213b9fc9352aba53
diff --git a/core/product.mk b/core/product.mk
index f242e82..a9af325 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -133,11 +133,14 @@
 #  3. Records that we've visited this node, in ALL_PRODUCTS
 #
 define inherit-product
+  $(if $(findstring ../,$(1)),\
+    $(eval np := $(call normalize-paths,$(1))),\
+    $(eval np := $(strip $(1))))\
   $(foreach v,$(_product_var_list), \
-      $(eval $(v) := $($(v)) $(INHERIT_TAG)$(strip $(1)))) \
+      $(eval $(v) := $($(v)) $(INHERIT_TAG)$(np))) \
   $(eval inherit_var := \
       PRODUCTS.$(strip $(word 1,$(_include_stack))).INHERITS_FROM) \
-  $(eval $(inherit_var) := $(sort $($(inherit_var)) $(strip $(1)))) \
+  $(eval $(inherit_var) := $(sort $($(inherit_var)) $(np))) \
   $(eval inherit_var:=) \
   $(eval ALL_PRODUCTS := $(sort $(ALL_PRODUCTS) $(word 1,$(_include_stack))))
 endef