shim: don't let build modify shim.config

Currently building the shim will modify shim.config in case some config
option was added or modified in the hypervisor.

Avoid that by copying shim.config to an intermediate file instead.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/firmware/xen-dir/Makefile

@@ -41,16 +41,12 @@ linkfarm.stamp: $(DEP_DIRS) $(DEP_FILES) FORCE
 $(D): linkfarm.stamp
 	$(MAKE) -C $(D)/xen distclean
 
-.PHONY: shim-%config
-shim-%config: $(D) FORCE
-	$(MAKE) -C $(D)/xen $*config \
-		XEN_CONFIG_EXPERT=y \
-		KCONFIG_CONFIG=$(CURDIR)/shim.config
+$(D)/xen/.config: shim.config $(D)
+	cp $< $@
+	$(MAKE) -C $(@D) olddefconfig XEN_CONFIG_EXPERT=y
 
-xen-shim: $(D) shim-olddefconfig
-	$(MAKE) -C $(D)/xen build \
-		XEN_CONFIG_EXPERT=y \
-		KCONFIG_CONFIG=$(CURDIR)/shim.config
+xen-shim: $(D)/xen/.config
+	$(MAKE) -C $(<D) build XEN_CONFIG_EXPERT=y
 	ln -sf $(D)/xen/xen $@
 	ln -sf $(D)/xen/xen-syms $@-syms