ci: add Windows builds using MinGW toolchain

This commit implements Windows testing and builds using MinGW toolchain.
Some details about the implementation:

- DLLs are built within CI from Microsoft's vcpkg repository as it appears
  to be the most reliable source for pinned versions out there.
- MinGW toolchain comes from https://github.com/niXman/mingw-builds-binaries
  as they provide a toolchain with little to no extras, reducing variables
  and binary surface in our builds. This toolchain targets UCRT runtime, which
  is bundled with Windows 10 and above.

.github/actions/setup-mingw/action.yml

@@ -0,0 +1,33 @@
+name: Setup MinGW environment
+description: Download and setup MinGW environment for Windows
+inputs:
+  mingw-version:
+    description: The release tag from niXman/mingw-builds-binaries to use
+    required: false
+    default: "13.2.0-rt_v11-rev1"
+
+runs:
+  using: "composite"
+  steps:
+    - if: runner.os != 'Windows'
+      name: Error when used on non-Windows runners
+      run: |
+        echo "::error::This action does not support $RUNNER_OS"
+        exit 1
+      shell: bash
+
+    - name: Download from niXman/mingw-builds-binaries
+      id: download
+      uses: robinraju/[email protected]
+      with:
+        repository: niXman/mingw-builds-binaries
+        tag: ${{ inputs.mingw-version }}
+        fileName: x86_64-*-win32-*-ucrt*.7z
+
+    - name: Extract MinGW and add to PATH
+      run: |
+        7z x "$MINGW_ARCHIVE"
+        echo "$RUNNER_TEMP/mingw32/bin" >> "$GITHUB_PATH"
+      shell: bash
+      env:
+        MINGW_ARCHIVE: ${{ fromJson(steps.download.outputs.downloaded_files)[0] }}

.github/workflows/ci.yml

@@ -92,6 +92,10 @@ jobs:
             {
               "name": "macOS",
               "runner": "macos-11"
+            },
+            {
+              "name": "Windows",
+              "runner": "windows-2019"
             }
           ]
           EOF
@@ -123,6 +127,28 @@ jobs:
       - name: Enable annotations
         run: echo "::add-matcher::.github/nim-problem-matcher.json"
 
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./.github/actions/setup-mingw
+
+      - name: Install dependencies (Windows)
+        if: runner.os == 'Windows'
+        uses: johnwason/vcpkg-action@v6
+        with:
+          pkgs: >-
+            pcre
+            sqlite3
+          triplet: x64-mingw-dynamic-release
+          extra-args: --host-triplet=x64-mingw-dynamic-release
+          revision: 2024.01.12
+          github-binarycache: true
+
+      - name: Install DLLs (Windows)
+        if: runner.os == 'Windows'
+        run: |
+          cp vcpkg/install/bin/libsqlite3.dll bin/sqlite3.dll
+          cp vcpkg/install/bin/libpcre.dll bin/pcre64.dll
+
       - name: Build release binaries
         run: ./koch.py all-strict
 
@@ -180,6 +206,10 @@ jobs:
         run: |
           brew update
 
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./.github/actions/setup-mingw
+
       - name: Run tester
         run: ./koch.py test --batch:'${{ matrix.batch }}_${{ matrix.total_batch }}' --tryFailing all
 
@@ -207,6 +237,10 @@ jobs:
 
       - uses: ./.github/actions/download-compiler
 
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./.github/actions/setup-mingw
+
       - name: Enable annotations
         run: echo "::add-matcher::.github/nim-problem-matcher.json"
 
@@ -227,6 +261,10 @@ jobs:
 
       - uses: ./.github/actions/download-compiler
 
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./.github/actions/setup-mingw
+
       - name: Enable annotations
         run: echo "::add-matcher::.github/nim-problem-matcher.json"
 
@@ -269,6 +307,17 @@ jobs:
     runs-on: ${{ matrix.target.runner }}
 
     steps:
+      - name: Get actions
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          path: git-src
+          sparse-checkout: .github/actions
+
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./git-src/.github/actions/setup-mingw
+
       - name: Download source archive
         uses: actions/download-artifact@v4
         with:
@@ -298,7 +347,11 @@ jobs:
       - id: package
         name: Create release package
         run: |
-          ./koch.py unixrelease
+          if [[ "$RUNNER_OS" == Windows ]]; then
+            ./koch.py winrelease
+          else
+            ./koch.py unixrelease
+          fi
 
           archive=build/archive/$(jq -r .name build/archive/archive.json)
           # Rename the archive manifest to avoid collision with other artifacts
@@ -340,6 +393,10 @@ jobs:
 
       - uses: ./.github/actions/download-compiler
 
+      - name: Install MinGW (Windows)
+        if: runner.os == 'Windows'
+        uses: ./.github/actions/setup-mingw
+
       - name: Enable annotations
         run: echo "::add-matcher::.github/nim-problem-matcher.json"
 
@@ -357,7 +414,11 @@ jobs:
       - id: package
         name: Create release package
         run: |
-          ./koch.py unixrelease
+          if [[ "$RUNNER_OS" == Windows ]]; then
+            ./koch.py winrelease
+          else
+            ./koch.py unixrelease
+          fi
 
           archive=build/archive/$(jq -r .name build/archive/archive.json)
           # Rename the archive manifest to avoid collision with other artifacts