Make ghc-in-ghci support Hadrian

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

1 files changed, 14 insertions, 4 deletions

diff --git a/utils/ghc-in-ghci/run.sh b/utils/ghc-in-ghci/run.sh
index 521458f67d..cb0ab0777d 100755
--- a/utils/ghc-in-ghci/run.sh
+++ b/utils/ghc-in-ghci/run.sh
@@ -23,10 +23,20 @@
 # If you don't want to wait for `:load Main`, since you want to load some other
 # module, then you can use `Ctrl+C` to cancel the initial load.
 
-
-export _GHC_TOP_DIR=./inplace/lib
-
-exec ./inplace/bin/ghc-stage2 \
+# Look in two common locations for a GHC installation (the results of using
+# the make- and Hadrian-based build systems, respectively).
+if [ -d ./inplace/lib ]; then
+  GHC_BIN=./inplace/bin/ghc-stage2
+  _GHC_TOP_DIR=./inplace/lib
+elif [ -d ./_build/stage1/lib ]; then
+  GHC_BIN=./_build/stage1/bin/ghc
+  _GHC_TOP_DIR=./_build/stage1/lib
+else
+  echo "Could not find GHC installation"
+  exit 1
+fi
+
+exec ${GHC_BIN} \
     --interactive \
     -ghci-script ./utils/ghc-in-ghci/settings.ghci \
     -ghci-script ./utils/ghc-in-ghci/load-main.ghci \