prevent Ruby tests getting stuck in OpenBSD

fifo-fail.diff

Some of Ruby's tests get stuck in OpenBSD.
This is because of OpenBSD's bug.  FIFO gets stuck.

This patch causes all FIFO tests to fail,
so I can run `make test-all` and `make test-spec` in OpenBSD.

Jeremy Evans (who knows OpenBSD better than me)
described the bug here: https://bugs.ruby-lang.org/issues/13875#note-7

diff --git a/spec/ruby/spec_helper.rb b/spec/ruby/spec_helper.rb
index c275e320ec..0266760ecb 100644
--- a/spec/ruby/spec_helper.rb
+++ b/spec/ruby/spec_helper.rb
@@ -1,3 +1,15 @@
+class << File
+  undef mkfifo
+  def mkfifo(*args) fail 'fifo bug' end
+end
+module Kernel
+  undef system
+  def system(*args, &block)
+    fail 'fifo bug' if /mkfifo/ =~ args[0]
+    Kernel.system(*args, &block)
+  end
+end
+
 use_realpath = File.respond_to?(:realpath)
 root = File.dirname(__FILE__)
 dir = "fixtures/code"
diff --git a/test/lib/test/unit.rb b/test/lib/test/unit.rb
index afdd5de00b..6b4c125501 100644
--- a/test/lib/test/unit.rb
+++ b/test/lib/test/unit.rb
@@ -1,4 +1,9 @@
 # frozen_string_literal: true
+class << File
+  undef mkfifo
+  def mkfifo(*args) fail 'fifo bug' end
+end
+
 begin
   gem 'minitest', '< 5.0.0' if defined? Gem
 rescue Gem::LoadError