stack.yaml: Update to latest resolver

caffe35e · Hans-Peter Deifel · b2bc5a20 · caffe35e
Commit caffe35e authored 6 years ago by Hans-Peter Deifel
--- a/stack.yaml
+++ b/stack.yaml
@@ -15,7 +15,7 @@
 # resolver:
 #  name: custom-snapshot
 #  location: "./custom-snapshot.yaml"
-resolver: lts-12.18
+resolver: lts-12.20

 # User packages to be built.
 # Various formats can be used as shown in the example below.