Fix xcheck

[H . J . Lu]

--- libc/manual/Makefile.xcheck	Tue Aug 28 08:29:53 2001
+++ libc/manual/Makefile	Sat Apr 20 17:03:47 2002
@@ -234,7 +234,7 @@ subdir_%: ;
 # ../Rules defines them for code subdirectories; for us, they are no-ops.
 # None of these should be `subdir_TARGET'; those targets are transformed
 # by the implicit rule above into `TARGET' deps.
-glibc-targets	:= lib objects objs others tests lint.out \
+glibc-targets	:= lib objects objs others tests xtests lint.out \
 		   echo-headers echo-distinfo
 .PHONY: $(glibc-targets)
 $(glibc-targets):