Ignore wait-forked-but-failed-child

Test will be fixed in #19588

Author: sfackler

src/test/run-pass/wait-forked-but-failed-child.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-test
 
 extern crate libc;