test: XFAIL lib-box on stage0. Upstream LLVM doesn't have the library reading patch yet.

Author: pcwalton

src/test/run-pass/drop-parametric-closure-with-bound-box.rs

@@ -1,3 +1,5 @@
+// xfail-stage0
+
 fn f[T](@int i, &T t) {}
 
 fn main() {

src/test/run-pass/lib-box.rs

@@ -1,3 +1,5 @@
+// xfail-stage0
+
 use std;
 import std.Box;