Add Windows to CI matrix using MSYS2

Author: gistrec

.github/workflows/tests.yml

@@ -11,13 +11,24 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    defaults:
+      run:
+        shell: ${{ matrix.os == 'windows-latest' && 'msys2 {0}' || 'bash' }}
 
     steps:
       - uses: actions/checkout@v4
         with:
           submodules: recursive
 
+      - name: Set up MSYS2 (Windows)
+        if: runner.os == 'Windows'
+        uses: msys2/setup-msys2@v2
+        with:
+          msystem: MINGW64
+          install: mingw-w64-x86_64-gcc make mingw-w64-x86_64-gtest
+
       - name: Install dependencies (Linux)
         if: runner.os == 'Linux'
         run: |