Revert to GHC 8.2/LTS-11, use a custom snapshot

Note that the previous workaround for #4125
should no longer be necessary because:

1. Stack 1.9 will not suffer from that bug
2. To my knowledge, custom snapshots never suffered from that bug

Guess we'll find out when Travis takes a crack at this though!

snapshot.yaml

@@ -0,0 +1,17 @@
+resolver: lts-11.19
+name: snapshot-for-building-stack-with-ghc-8.2.2
+
+packages:
+- Cabal-2.2.0.1@rev:0
+- cabal-install-2.2.0.0@rev:1
+- resolv-0.1.1.1@rev:0
+- infer-license-0.2.0@rev:0
+- hpack-0.29.6@rev:0
+- http-api-data-0.3.8.1@rev:0
+- githash-0.1.0.1@rev:0
+- rio-orphans-0.1.1.0@sha256:15600084c56ef4e1f22ac2091d10fa6ed62f01f531d819c6a5a19492212a76c9
+
+flags:
+  cabal-install:
+    # https://github.com/haskell/cabal/issues/4883
+    native-dns: false

stack.yaml

@@ -1,4 +1,4 @@
-resolver: lts-12.0
+resolver: snapshot.yaml
 
 # docker:
 #   enable: true
@@ -16,10 +16,6 @@ flags:
   stack:
     hide-dependency-versions: true
     supported-build: true
-extra-deps:
-- infer-license-0.2.0@rev:0
-- hpack-0.29.6@rev:0
-- githash-0.1.0.1@rev:0
 
 ghc-options:
    "$locals": -fhide-source-paths