Move ghc install to avoid errors

Author: jneira

.azure/windows-stack.yml

@@ -48,6 +48,7 @@ jobs:
   - bash: |
       source .azure/windows-stack.bashrc
       stack setup --stack-yaml $(YAML_FILE)
+      stack setup --resolver=lts-13.20 # for liquidhaskell
     displayName: Install GHC
   - bash: |
       source .azure/windows-stack.bashrc
@@ -87,7 +88,6 @@ jobs:
     displayName: "Install Runtime Test-Dependencies: z3"
   - bash: |
       source .azure/windows-stack.bashrc
-      stack setup --resolver=lts-13.20 
       stack install --resolver=lts-13.20 liquid-fixpoint-0.8.0.2 liquidhaskell-0.8.6.2
     displayName: "Install Runtime Test-Dependencies: liquidhaskell"
   - bash: |