Overriding GHC doesn't apply to tools

[TravisWhitaker]

I accidentally created this issue without a description, but @hamishmack replied with the PR with the fix before I could finish typing the description! Wow, thanks!

[hamishmack]

Should be fixed in #738

[TravisWhitaker]

Yep, looks like that'll do it. Thanks for the (literally instant) response!

[hamishmack]

#738 is merged. Let us know if it does not work as expected. Check the change log entry for details of the breaking interface changes that were included.