x86: minor polishing to top-level arch Makefile

Use build target when creating compatibility link, and use $(boot)
where possible.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/Makefile

@@ -210,12 +210,12 @@ all: bzImage
 
 # KBUILD_IMAGE specify target image being built
                     KBUILD_IMAGE := $(boot)/bzImage
-zImage zlilo zdisk: KBUILD_IMAGE := arch/x86/boot/zImage
+zImage zlilo zdisk: KBUILD_IMAGE := $(boot)/zImage
 
 zImage bzImage: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
 	$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
-	$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/bzImage
+	$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
 
 compressed: zImage