Make lts-12 the default stack configuration in appveyor to avoid build timeouts (#893)

* Use lts-12
* Remove cache on fail and add workaround to fix build with stack
* Add dhall-lsp-server to lts-12
* Commenting out default stack.yaml
* Bump up megaparsec version

appveyor.yml

@@ -9,9 +9,15 @@ branches:
 environment:
   STACK_ROOT: C:\sr
   STACK_VERSION: 1.9.3
-
+  # Override the temp directory to avoid sed escaping issues
+  # See https://github.com/haskell/cabal/issues/5386
+  TMP: c:\tmp
+  
   matrix:
-    - STACK_YAML: stack.yaml
+    # Commenting out for now default stack (lts-13) cause
+    # compilations times are reaching appveyor default build timeout
+    # - STACK_YAML: stack.yaml
+    - STACK_YAML: stack-lts-12.yaml
     - STACK_YAML: stack-lts-6.yaml
 
 install:

stack-lts-12.yaml

@@ -4,13 +4,17 @@ packages:
   - dhall-bash
   - dhall-json
   - dhall-text
+  - dhall-lsp-server
 extra-deps:
-  - megaparsec-7.0.3
+  - megaparsec-7.0.4
   - repline-0.2.0.0
   - serialise-0.2.1.0
   - neat-interpolation-0.3.2.4
-  - dotgen-0.4.2@sha256:309b7cc8a3593a8e48bee7b53020d5f72db156d58edf78a0214f58fbb84b292b
+  - dotgen-0.4.2
   - cborg-json-0.2.1.0
+  - base-noprelude-4.11.1.0
+  - haskell-lsp-0.8.1.0
+  - haskell-lsp-types-0.8.0.1
 nix:
   packages:
     - ncurses