OldModLocation fails on Windows

As of 3028f75c the OldModLocation test is broken on Windows:

--- ghc-api/downsweep/OldModLocation.run/OldModLocation.stderr.normalised	2019-06-04 14:40:26.326075000 +0000
+++ ghc-api/downsweep/OldModLocation.run/OldModLocation.run.stderr.normalised	2019-06-04 14:40:26.328029200 +0000
@@ -1 +1 @@
-[Just "A.hs",Just "mydir/B.hs"]
+[Just "A.hs",Just "mydir//B.hs"]

This is strange; I don't recall ever noticing this double-delimiter issue before on Windows. @Phyx, do you have any idea what might cause this?

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information