Use msys2 on Windows in github actions

Author: coot

.github/workflows/haskell.yml

@@ -12,17 +12,70 @@ jobs:
         ghc: ["8.10.7", "9.2.2"]
         os: [ubuntu-latest, macos-latest, windows-latest]
 
+    defaults:
+      run:
+        shell: ${{ matrix.os == 'windows-latest' && 'msys2 {0}' || 'bash' }}
+
     steps:
+    - name: "WIN: Setup MSYS2 and libraries"
+      if: runner.os == 'Windows'
+      uses: msys2/setup-msys2@v2
+      with:
+        update: true
+        install: >-
+          base-devel
+          autoconf-wrapper
+          autoconf
+          automake
+          libtool
+          make
+          git
+          mingw-w64-x86_64-jq
+
     - name: Set cache version
       run: echo "CACHE_VERSION=pu4Aevoo" >> $GITHUB_ENV
 
-    - name: "Setup Haskell"
+    - name: "LINUX: Setup Haskell"
       uses: haskell/actions/setup@v1
+      if: runner.os != 'Windows'
       id: setup-haskell
       with:
         ghc-version: ${{ matrix.ghc }}
         cabal-version: 3.6.2.0
 
+    - name: "WIN: Setup Haskell"
+      id: win-setup-haskell
+      if: runner.os == 'Windows'
+      run: |
+        # see https://gitlab.haskell.org/haskell/ghcup-hs/-/blob/master/scripts/bootstrap/bootstrap-haskell
+        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | \
+          BOOTSTRAP_HASKELL_NONINTERACTIVE=1 \
+          BOOTSTRAP_HASKELL_ADJUST_CABAL_CONFIG=1 \
+          BOOTSTRAP_HASKELL_ADJUST_BASHRC=1 \
+          BOOTSTRAP_HASKELL_GHC_VERSION="${{ matrix.ghc }}" \
+          BOOTSTRAP_HASKELL_CABAL_VERSION="3.6.2.0" \
+          sh
+
+        # MSYS2 doesn't inherit $GITHUB_PATH so this is needed
+        cat <(echo "source /c/ghcup/env") ~/.bashrc > ~/.bashrc.new
+        mv ~/.bashrc.new ~/.bashrc
+
+        source ~/.bashrc
+
+        # There is an issue with crt libraries, fixed by prepending the ghc
+        # mingw32 libraries directory to every other library directory.
+        echo "# Original cabal config extra-lib-dirs"
+        grep extra-lib-dirs /c/cabal/config
+
+        sed -i 's/C:\\msys64\\mingw64\\lib/C:\\ghcup\\ghc\\8.10.7\\mingw\\x86_64-w64-mingw32\\lib, C:\\msys64\\mingw64\\lib/g' /c/cabal/config
+
+        echo "# Modified cabal config extra-lib-dirs"
+        grep extra-lib-dirs /c/cabal/config
+
+        ghc --version
+        cabal --version
+        echo "::set-output name=cabal-store::$(dirname $(cabal --help | tail -1 | tr -d ' '))\\store"
+
     - uses: actions/checkout@v2
 
     - name: "Configure cabal.project.local"