Fix Makefile to use correct script path.

iphydf · iphydf · commit 99776f94be1d · 2018-08-12T08:53:27.000Z
This makes a plain "make" in the project root work.
diff --git a/Makefile b/Makefile
@@ -1,2 +1,2 @@
 heroku:
-	$(MAKE) -f build-host
+	$(MAKE) -f scripts/build-host
