Fix the kernel build when we have multi-part objects both in $(obj-y)

and $(obj-m).

Before, we would have built (though not linked) the individual objects
for multi-part modules even when building vmlinux and vice versa.

Rules.make

@@ -126,11 +126,23 @@ endif
 
 # for make >= 3.78 the following is cleaner:
 # multi-used := $(foreach m,$(obj-y) $(obj-m), $(if $($(basename $(m))-objs), $(m)))
-multi-used := $(sort $(foreach m,$(obj-y) $(obj-m),$(patsubst %,$(m),$($(basename $(m))-objs))))
-ld-multi-used := $(filter-out $(list-multi),$(multi-used))
-ld-multi-objs := $(foreach m, $(ld-multi-used), $($(basename $(m))-objs))
+multi-used-y := $(sort $(foreach m,$(obj-y),$(patsubst %,$(m),$($(basename $(m))-objs))))
+multi-used-m := $(sort $(foreach m,$(obj-m),$(patsubst %,$(m),$($(basename $(m))-objs))))
+ld-multi-used-y := $(filter-out $(list-multi),$(multi-used-y))
+ld-multi-used-m := $(filter-out $(list-multi),$(multi-used-m))
+ld-multi-objs-y := $(foreach m, $(ld-multi-used-y), $($(basename $(m))-objs))
+ld-multi-objs-m := $(foreach m, $(ld-multi-used-m), $($(basename $(m))-objs))
+
+$(ld-multi-used-y) : %.o: $(ld-multi-objs-y)
+	rm -f $@
+	$(LD) $(EXTRA_LDFLAGS) -r -o $@ $(filter $($(basename $@)-objs), $^)
+	@ ( \
+	    echo 'ifeq ($(strip $(subst $(comma),:,$(LD) $(EXTRA_LDFLAGS) $($(basename $@)-objs)),$$(strip $$(subst $$(comma),:,$$(LD) $$(EXTRA_LDFLAGS) $$($(basename $@)-objs)))))' ; \
+	    echo 'FILES_FLAGS_UP_TO_DATE += $@' ; \
+	    echo 'endif' \
+	) > $(dir $@)/.$(notdir $@).flags
 
-$(ld-multi-used) : %.o: $(ld-multi-objs)
+$(ld-multi-used-m) : %.o: $(ld-multi-objs-m)
 	rm -f $@
 	$(LD) $(EXTRA_LDFLAGS) -r -o $@ $(filter $($(basename $@)-objs), $^)
 	@ ( \