Fix installing in parallel

http://bugs.gentoo.org/180672

--- include/Makefile
+++ include/Makefile
@@ -9,9 +9,9 @@
 LSRCFILES = builddefs.in buildmacros buildrules dmapi_kern.h
 LDIRT = xfs
 
-default install :
-	rm -f xfs
-	$(LN_S) . xfs
+xfs:
+	$(LN_S) . $@
+default install : xfs
 
 include $(BUILDRULES)