`ruby.exe: invalid option -V` due to bad `RUBYOPT` and `VAGRANT_RUBYOPT_SAVED`

[Torben Knerr]

When using Vagrant for a while I get this strange error message:

```

D:\Repos\_github\cookbooks-gitlab>bundle exec berks install --path cookbooks

ruby.exe: invalid option -V  (-h will show valid options) (RuntimeError)

```

I can't reliably reproduce it, it just happens sometimes.

However, the problem occurs as soon as the `RUBYOPT` env var gets set to a bad value. I don't know when this happens, but looking at the environment it looks like there's something wrong with these vars:

```

C:\>set

...

RUBYOPT=VAGRANT_RUBYOPT_SAVED

VAGRANT_RUBYOPT_SAVED=VAGRANT_RUBYOPT_SAVED

...

```

Should that be `RUBYOPT=%VAGRANT_RUBYOPT_SAVED%` ???

Unsetting the `RUBYOPT` and `VAGRANT_RUBYOPT_SAVED` temporarily fixes the symptoms until it occurs again.

I'm on Windows, Vagrant 1.2.2.

Anyone else experiencing this?