kbuild: get rid of kernel/ prefix from in-tree modules.{order,builtin}

Removing the 'kernel/' prefix will make our life easier because we can
simply do 'cat modules.order' to get all built modules with full paths.

Currently, we parse the first line of '*.mod' files in $(MODVERDIR).
Since we have duplicated functionality here, I plan to remove MODVERDIR
entirely.

In fact, modules.order is generated also for external modules in a
broken format. It adds the 'kernel/' prefix to the absolute path of
the module, like this:

  kernel//path/to/your/external/module/foo.ko

This is fine for now since modules.order is not used for external
modules. However, I want to sanitize the format everywhere towards
the goal of removing MODVERDIR.

We cannot change the format of installed module.{order,builtin}.
So, 'make modules_install' will add the 'kernel/' prefix while copying
them to $(MODLIB)/.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/Makefile b/Makefile
index b74a6e9..396cd5e 100644
--- a/Makefile
+++ b/Makefile
@@ -1329,8 +1329,8 @@
 		rm -f $(MODLIB)/build ; \
 		ln -s $(CURDIR) $(MODLIB)/build ; \
 	fi
-	@cp -f $(objtree)/modules.order $(MODLIB)/
-	@cp -f $(objtree)/modules.builtin $(MODLIB)/
+	@sed 's:^:kernel/:' modules.order > $(MODLIB)/modules.order
+	@sed 's:^:kernel/:' modules.builtin > $(MODLIB)/modules.builtin
 	@cp -f $(objtree)/modules.builtin.modinfo $(MODLIB)/
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst