ci: add cygwin test on MSYS2

Author: Berrysoft

.github/workflows/libloading.yml

@@ -65,6 +65,26 @@ jobs:
         env:
           TARGET: ${{ matrix.rust_target}}
 
+  msys2-test:
+    runs-on: windows-latest
+    strategy:
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@v2
+      - run: rustup install nightly --profile=minimal
+      - run: rustup default nightly
+      - uses: msys2/setup-msys2@v2
+        with:
+          release: false
+          install: gcc
+      - run: mkdir .cargo
+      - run: echo "[target.x86_64-pc-cygwin]" | Out-File -FilePath .cargo/config.toml -Append
+      - run: echo 'linker = "x86_64-pc-msys-gcc.exe"' | Out-File -FilePath .cargo/config.toml -Append
+      - run: echo "INPUT(libmsys-2.0.a)" | Out-File -FilePath "C:\msys64\usr\lib\libcygwin.a"
+      - run: cargo test --target x86_64-pc-cygwin -Zbuild-std
+        env:
+          TARGET: x86_64-pc-windows-msvc
+
   bare-cross-build:
     runs-on: ubuntu-latest
     strategy: