ci : add msys2 build

.github/workflows/build.yml

@@ -143,7 +143,7 @@ jobs:
 			  make
 			  ctest --output-on-failure
 
-    Emscripten:
+	emscripten:
 	  runs-on: ubuntu-18.04
 
 	  strategy:
@@ -174,3 +174,25 @@ jobs:
 			  popd
 			  emcmake cmake . -DCMAKE_BUILD_TYPE=${{ matrix.build }}
 			  make && ctest --output-on-failure
+
+jobs:
+  windows-msys2:
+	runs-on: windows-latest
+	defaults:
+	  run:
+		shell: msys2 {0}
+		steps:
+		  - uses: actions/checkout@v2
+		  - uses: msys2/setup-msys2@v2
+			with:
+			  msystem: MINGW64
+			  update: true
+			  install: cmake make mingw-w64-x86_64-dlfcn mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL2
+
+		  - name: Configure
+			run: cmake . -DCMAKE_BUILD_TYPE=${{ matrix.build }}
+
+		  - name: Build
+			run: |
+			  make
+			  ctest --output-on-failure