Add HscTypes.hi-boot-6 so builds with older GHCs succeed

diff --git a/compiler/main/HscTypes.hi-boot-6 b/compiler/main/HscTypes.hi-boot-6
new file mode 100644 (file)
index 0000000..7b4a7d1
--- /dev/null
+++ b/compiler/main/HscTypes.hi-boot-6
@@ -0,0 +1,3 @@
+module HscTypes where
+
+data Session