Tamar Christina authored Feb 23, 2017 and Ben Gamari committed Feb 23, 2017

GHC and ghc-pkg make some pretty hard assumptions about where they're
running on Windows. They assume that they are always running from
`foo/bin/ghc.exe` and that to find the `lib` folder they can drop
`bin/ghc.exe` from the base path and append `lib`.

This is already false for the testsuite, which when testing thenbindist
 has one test which puts the binaries in `inplace/test   spaces`.

For some reason before this was either being skipped or mysteriously 
passing.
But as of `2017.02.11` our luck ran out.

the testsuite triggers a failure such as those in #13310

Let's soften the assumption and just check that `../lib` exists instead.

80 chars

Test Plan: ./validate

Reviewers: austin, erikd, bgamari

Reviewed By: bgamari

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D3158