-__c_flags = $(call addtree,-I$(obj)) $(call flags,_c_flags)
-__a_flags = $(call flags,_a_flags)
-__cpp_flags = $(call flags,_cpp_flags)
+__c_flags = $(if $(obj),-I$(srctree)/$(src) -I$(obj)) \
+ $(call flags,_c_flags)
+__a_flags = $(call flags,_a_flags)
+__cpp_flags = $(call flags,_cpp_flags)