+
+# Usually want the debug version
+ifeq "$(BootingFromHc)" "NO"
+GhcRTSWays += debug
+endif
+
+# Want the threaded versions unless we're unregisterised
+# Defer the check until later by using $(if..), because GhcUnregisterised might
+# be set in build.mk, which hasn't been read yet.
+GhcRTSWays += $(if $(findstring NO, $(GhcUnregisterised)),thr thr_p thr_debug,)
+
+# We can only build GHCi threaded if we have a threaded RTS:
+ifneq "$(findstring thr, $(GhcRTSWays))" ""
+GhcThreaded=YES