Try newer GHC on Appveyor

appveyor.yml

@@ -21,8 +21,8 @@ install:
   # Using '-y' and 'refreshenv' as a workaround to:
   # https://github.com/haskell/cabal/issues/3687
   - choco source add -n mistuke -s https://www.myget.org/F/mistuke/api/v2
-  - choco install -y ghc --version 8.0.2 --ignore-dependencies
-  - choco install -y cabal-head -pre
+  - choco install -y cabal --version 3.0.0.0
+  - choco install -y ghc --version 8.6.5
   - refreshenv
   - cabal --version
   - cabal %CABOPTS% update
@@ -30,7 +30,7 @@ install:
 
 environment:
   global:
-    CABOPTS:  "--store-dir=C:\\SR"
+    CABOPTS: --store-dir=C:\\SR --http-transport=plain-http
     # Remove cache, there is no button on the web
     # https://www.appveyor.com/docs/build-cache/#skipping-cache-operations-for-specific-build
     APPVEYOR_CACHE_SKIP_RESTORE: true
@@ -48,7 +48,7 @@ build_script:
   - cabal %CABOPTS% new-test Cabal
   - appveyor-retry cabal %CABOPTS% new-build exe:cabal exe:cabal-tests --only-dependencies
   - cabal %CABOPTS% new-build exe:cabal
-  - cabal %CABOPTS% new-run cabal-tests -- -j3 --with-cabal=dist-newstyle\build\x86_64-windows\ghc-8.0.2\cabal-install-3.1.0.0\x\cabal\build\cabal\cabal.exe
+  - cabal %CABOPTS% new-run cabal-tests -- -j3 --with-cabal=dist-newstyle\build\x86_64-windows\ghc-8.6.5\cabal-install-3.1.0.0\x\cabal\build\cabal\cabal.exe
   - appveyor-retry cabal %CABOPTS% new-build cabal-install:tests --only-dependencies
   - cd cabal-install
   - cabal %CABOPTS% new-run cabal-install:memory-usage-tests