Summary:
Currently, `ghc-in-ghci` is hard-coded to only support
the installation path of the `make`-based build system. There isn't
a fundamental reason why this must be the case, however—it's just a
matter of communicating which directories to look into.

For the time being, I've hacked `utils/ghc-in-ghci/run.sh` to just
check the default Hadrian installation path in addition to the `make`
one. Disclaimer: I'm not well-versed in `bash`-fu, so it's possible
that there is a better way to accomplish what I'm setting out to do.
Suggestions welcome.

Test Plan: ./utils/ghc-in-ghci/run.sh

Reviewers: alpmestan, bgamari

Reviewed By: alpmestan

Subscribers: rwbarton, carter

Differential Revision: https://phabricator.haskell.org/D5390