add xfail-fast directive

Author: nikomatsakis

src/test/run-pass/crate-method-reexport-grrrrrrr.rs

@@ -2,6 +2,7 @@
 // name_pool::methods impl in the other crate is reachable from this
 // crate.
 
+// xfail-fast
 // aux-build:crate-method-reexport-grrrrrrr2.rs
 
 use crate_method_reexport_grrrrrrr2;
@@ -12,4 +13,4 @@ fn main() {
     x.cx();
     let y = ();
     y.add("hi");
-}
+}