Full AppVeyor build with tests

.appveyor.sh

 # Configure the environment
 MSYSTEM=MINGW64
-THREADS=3
+THREADS=9
 SKIP_PERF_TESTS=YES
-BUILD_FLAVOUR=quick
+BUILD_FLAVOUR=
 source /etc/profile || true # a terrible, terrible workaround for msys2 brokenness
 
 # Don't set -e until after /etc/profile is sourced
@@ -11,45 +11,27 @@ cd $APPVEYOR_BUILD_FOLDER
 
 case "$1" in
     "prepare")
-        # Bring msys up-to-date
-        # However, we current don't do this: generally one must restart all
-        # msys2 processes when updating the msys2 runtime, which this may do. We can't
-        # easily do this and therefore do simply don't update.
-        #pacman --noconfirm -Syuu
-
-        # Install basic build dependencies
-        pacman --noconfirm -S --needed git tar bsdtar binutils autoconf make xz curl libtool automake python python2 p7zip patch mingw-w64-$(uname -m)-python3-sphinx mingw-w64-$(uname -m)-tools-git
-
         # Prepare the tree
         git config remote.origin.url git://github.com/ghc/ghc.git
         git config --global url."git://github.com/ghc/packages-".insteadOf git://github.com/ghc/packages/
         git submodule init
         git submodule --quiet update --recursive
-
-        # Install build dependencies
-        wget -q -O - https://downloads.haskell.org/~ghc/8.2.1/ghc-8.2.1-x86_64-unknown-mingw32.tar.xz | tar -xJ -C /mingw64 --strip-components=1
-        mkdir -p /usr/local/bin
-        wget -q -O - https://www.haskell.org/cabal/release/cabal-install-1.24.0.0/cabal-install-1.24.0.0-x86_64-unknown-mingw32.zip | bsdtar -xzf- -C /usr/local/bin
-        cabal update
-        cabal install -j --prefix=/usr/local alex happy
         ;;
-
     "build")
         # Build the compiler
         ./boot
-        ./configure --enable-tarballs-autodownload
         cat <<EOF >> mk/build.mk
         BuildFlavour=$BUILD_FLAVOUR
         ifneq "\$(BuildFlavour)" ""
         include mk/flavours/\$(BuildFlavour).mk
         endif
 EOF
+        ./configure --enable-tarballs-autodownload
         make -j$THREADS
         ;;
 
     "test")
-        # This does not finish in time.
-        # make fasttest THREADS=$THREADS
+        make test THREADS=$THREADS
         make binary-dist
         7z a ghc-windows.zip *.tar.xz
         ;;

appveyor.yml

 version: "{build}"
+build_cloud: ghc-gce-cloud
+image: GHC-GCE
 
 build:
   verbosity: normal
@@ -12,7 +14,6 @@ environment:
     MSYSTEM: MINGW64
     BIT: 64
 
-os: Visual Studio 2015
 deploy: off
 
 install: