ci: Add MSYS2 workflow on GitHub Actions

.github/workflows/msys2.yml

@@ -0,0 +1,28 @@
+name: MSYS2 Build
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    env:
+      PYTHONIOENCODING: "utf-8"
+    steps:
+    - uses: actions/checkout@master
+    - uses: msys2/setup-msys2@v2
+      with:
+        msystem: MINGW64
+        update: true
+        install: base-devel git mingw-w64-x86_64-meson mingw-w64-x86_64-ninja mingw-w64-x86_64-pkg-config mingw-w64-x86_64-python3 mingw-w64-x86_64-python3-pip mingw-w64-x86_64-toolchain
+    - name: Build
+      run: |
+        meson setup _build
+        meson compile -C _build
+        meson test -C _build