ia64: thin archives fix linking

The VDSO symbols can't be linked into built-in.o when building with
thin archives, so change this to linking a new object file that is
included into the built-in.o.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/ia64/kernel/Makefile.gate

 # The gate DSO image is built using a special linker script.
 
-targets += gate.so gate-syms.o gate.lds gate.o
+targets += gate.so gate.lds gate.o gate-dummy.o
+
+obj-y += gate-syms.o
 
 CPPFLAGS_gate.lds := -P -C -U$(ARCH)
 
@@ -12,13 +14,14 @@ GATECFLAGS_gate.so = -shared -s -Wl,-soname=linux-gate.so.1 \
 $(obj)/gate.so: $(obj)/gate.lds $(obj)/gate.o FORCE
 	$(call if_changed,gate)
 
-$(obj)/built-in.o: $(obj)/gate-syms.o
-$(obj)/built-in.o: ld_flags += -R $(obj)/gate-syms.o
-
-GATECFLAGS_gate-syms.o = -r
-$(obj)/gate-syms.o: $(obj)/gate.lds $(obj)/gate.o FORCE
+GATECFLAGS_gate-dummy.o = -r
+$(obj)/gate-dummy.o: $(obj)/gate.lds $(obj)/gate.o FORCE
 	$(call if_changed,gate)
 
+LDFLAGS_gate-syms.o := -r -R
+$(obj)/gate-syms.o: $(obj)/gate-dummy.o FORCE
+	$(call if_changed,ld)
+
 # gate-data.o contains the gate DSO image as data in section .data..gate.
 # We must build gate.so before we can assemble it.
 # Note: kbuild does not track this dependency due to usage of .incbin