Environment

• jruby 9.1.7.0 (2.3.1) 2017-01-11 68056ae OpenJDK 64-Bit Server VM 25.192-b26 on 1.8.0_192-b26 +jit [freebsd-x86_64]
• FreeBSD x220 12.0-RELEASE FreeBSD 12.0-RELEASE r341666 GENERIC amd64

Expected Behavior

I expect JRuby and MRI Ruby to return the same value - true - when File.stat.writable? is run on a writable directory (/tmp).

Actual Behavior

JRuby returns false, where MRI returns true:

➜  ~ ls -lad /tmp
drwxrwxrwt  21 root  wheel  1024  4 Mar 09:43 /tmp
➜  ~ RBENV_VERSION=2.5.1 irb
irb(main):001:0> File.stat('/tmp').writable?
=> true

➜  ~ ls -lad /tmp
drwxrwxrwt  21 root  wheel  1024  4 Mar 09:43 /tmp
➜  ~ RBENV_VERSION=jruby-9.1.7.0 irb
irb(main):001:0> File.stat('/tmp').writable?
=> false

This is causing many failures, including an inability to install Gems, because Dir::tmpdir is failing to find a writable tmpdir.