On FreeBSD omit the test to close a pipe while reading [ci skip]

bootstraptest/test_io.rb

@@ -83,6 +83,7 @@ assert_normal_exit %q{
   ARGF.set_encoding "foo"
 }
 
+/freebsd/ =~ RUBY_PLATFORM or
 10.times do
   assert_normal_exit %q{
     at_exit { p :foo }