build: save generated xen .config

Since we now support changing Xen options with Kconfig, we should save
the configuration that was used to build up Xen. This will save it in
/usr/lib/debug alongside xen-syms and call it xen-$(FULLVERSION).config

Suggested-by: Ian Campbell <ian.campbell@citrix.com>
Requested-by: Jan Beulich <jbeulich@suse.com> # the directory
Signed-off-by: Doug Goldstein <cardoe@cardoe.com>

xen/Makefile

@@ -58,6 +58,7 @@ _install: $(TARGET)$(CONFIG_XEN_INSTALL_SUFFIX)
 	ln -f -s $(T)-$(XEN_FULLVERSION)$(Z) $(D)$(BOOT_DIR)/$(T)$(Z)
 	[ -d "$(D)$(DEBUG_DIR)" ] || $(INSTALL_DIR) $(D)$(DEBUG_DIR)
 	$(INSTALL_DATA) $(TARGET)-syms $(D)$(DEBUG_DIR)/$(T)-syms-$(XEN_FULLVERSION)
+	$(INSTALL_DATA) $(KCONFIG_CONFIG) $(D)$(DEBUG_DIR)/$(T)-$(XEN_FULLVERSION).config
 	if [ -r $(TARGET).efi -a -n '$(EFI_DIR)' ]; then \
 		[ -d $(D)$(EFI_DIR) ] || $(INSTALL_DIR) $(D)$(EFI_DIR); \
 		$(INSTALL_DATA) $(TARGET).efi $(D)$(EFI_DIR)/$(T)-$(XEN_FULLVERSION).efi; \