kbuild: Generate modules.builtin in make modules_install

The previous approach didn't work if one did
make modules && make modules_install
Add modules.builtin as dependency of _modinst_, which is the target that
actually needs the file.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Makefile

@@ -1086,7 +1086,7 @@ ifdef CONFIG_MODULES
 
 # By default, build modules as well
 
-all: modules modules.builtin
+all: modules
 
 #	Build modules
 #
@@ -1104,7 +1104,7 @@ modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux)
 modules.builtin: $(vmlinux-dirs:%=%/modules.builtin)
 	$(Q)$(AWK) '!x[$$0]++' $^ > $(objtree)/modules.builtin
 
-%/modules.builtin: include/config/auto.conf | modules
+%/modules.builtin: include/config/auto.conf
 	$(Q)$(MAKE) $(modbuiltin)=$*
 
 
@@ -1117,7 +1117,7 @@ PHONY += modules_install
 modules_install: _modinst_ _modinst_post
 
 PHONY += _modinst_
-_modinst_:
+_modinst_: modules.builtin
 	@if [ -z "`$(DEPMOD) -V 2>/dev/null | grep module-init-tools`" ]; then \
 		echo "Warning: you may need to install module-init-tools"; \
 		echo "See http://www.codemonkey.org.uk/docs/post-halloween-2.6.txt";\