Test Windows cross-compilation on CI

.github/workflows/main.yml

@@ -11,7 +11,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        include:
+          - os: ubuntu-latest
+          - os: macos-latest
+          # cross-compile from Linux to Windows using mingw
+          - os: ubuntu-latest
+            env:
+              TARGET_TRIPLE: x86_64-pc-windows-gnu
 
     steps:
     - uses: actions/checkout@v2
@@ -36,6 +42,12 @@ jobs:
         path: target
         key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('rust-toolchain', '**/Cargo.lock') }}
 
+    - name: Install MinGW toolchain and wine
+      if: matrix.os == 'ubuntu-latest' && matrix.env.TARGET_TRIPLE == 'x86_64-pc-windows-gnu'
+      run: |
+        sudo apt-get install -y gcc-mingw-w64-x86-64 wine-stable
+        rustup target add x86_64-pc-windows-gnu
+
     - name: Prepare dependencies
       run: |
         git config --global user.email "user@example.com"
@@ -43,6 +55,8 @@ jobs:
         ./prepare.sh
 
     - name: Test
+      env:
+        TARGET_TRIPLE: ${{ matrix.env.TARGET_TRIPLE }}
       run: |
         # Enable backtraces for easier debugging
         export RUST_BACKTRACE=1
@@ -57,6 +71,7 @@ jobs:
       run: tar cvfJ cg_clif.tar.xz build
 
     - name: Upload prebuilt cg_clif
+      if: matrix.env.TARGET_TRIPLE != 'x86_64-pc-windows-gnu'
       uses: actions/upload-artifact@v2
       with:
         name: cg_clif-${{ runner.os }}

prepare.sh

@@ -2,7 +2,6 @@
 set -e
 
 rustup component add rust-src rustc-dev llvm-tools-preview
-rustup target add x86_64-pc-windows-gnu
 ./build_sysroot/prepare_sysroot_src.sh
 cargo install hyperfine || echo "Skipping hyperfine install"