package/pkg-generic.mk: only check for virtual package conflicts when building

The configuration checks should only be done when building so that
make allyespackageconfig && make source works.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 7231701a290ba447fde9807ba9d260022ddfc8e4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-generic.mk

@@ -1182,10 +1182,12 @@ ifeq ($$($$($(2)_KCONFIG_VAR)),y)
 
 # Ensure the calling package is the declared provider for all the virtual
 # packages it claims to be an implementation of.
+ifeq ($(BR_BUILDING),y)
 ifneq ($$($(2)_PROVIDES),)
 $$(foreach pkg,$$($(2)_PROVIDES),\
 	$$(eval $$(call virt-provides-single,$$(pkg),$$(call UPPERCASE,$$(pkg)),$(1))$$(sep)))
 endif
+endif
 
 # Register package as a reverse-dependencies of all its dependencies
 $$(eval $$(foreach p,$$($(2)_FINAL_ALL_DEPENDENCIES),\