um: merge Makefile-{i386,x86_64}

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/arch/um/Makefile b/arch/um/Makefile
index bd0587e..7492ee5 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -20,8 +20,18 @@
 
 MODE_INCLUDE	+= -I$(srctree)/$(ARCH_DIR)/include/shared/skas
 
+HEADER_ARCH 	:= $(SUBARCH)
+
+# Additional ARCH settings for x86
+ifeq ($(SUBARCH),i386)
+        HEADER_ARCH := x86
+endif
+ifeq ($(SUBARCH),x86_64)
+        HEADER_ARCH := x86
+endif
+
 include $(srctree)/$(ARCH_DIR)/Makefile-skas
-include $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH)
+include $(srctree)/$(ARCH_DIR)/Makefile-$(HEADER_ARCH)
 
 SHARED_HEADERS	:= $(ARCH_DIR)/include/shared
 ARCH_INCLUDE	:= -I$(srctree)/$(SHARED_HEADERS)