Update Makefile

diff --git a/ast b/ast
index 60043131318a6c664df13d3dabbe29da986da938..19979ef8587bc8ce9f49a0c470ef0c8c53756003 160000 (submodule)
--- a/ast
+++ b/ast
@@ -1 +1 @@
-Subproject commit 60043131318a6c664df13d3dabbe29da986da938
+Subproject commit 19979ef8587bc8ce9f49a0c470ef0c8c53756003