kbuild/i386: Add missing dependency in kernel/Makefile

I deleted this dependency during the clean-up, but
the this caused caused linking of vmlinux to fail for a
clean build

arch/i386/kernel/Makefile

@@ -58,6 +58,7 @@ $(obj)/vsyscall-%.so: $(src)/vsyscall.lds $(obj)/vsyscall-%.o FORCE
 # table and layout of the linked DSO.  With ld -R we can then refer to
 # these symbols in the kernel code rather than hand-coded addresses.
 extra-y += vsyscall-syms.o
+$(obj)/built-in.o: $(obj)/vsyscall-syms.o
 $(obj)/built-in.o: ld_flags += -R $(obj)/vsyscall-syms.o
 
 SYSCFLAGS_vsyscall-syms.o = -r