Add llvm-mingw installation for ARM64 cross-compilation

Added llvm-mingw installation step for ARM64 cross-compilation on Windows.

Author: dellis1972

.github/workflows/main.yml

@@ -29,6 +29,18 @@ jobs:
         shell: bash
         run:  |
           C:\\msys64\\usr\\bin\\bash.exe -c 'export PATH="/usr/bin:/mingw64/bin:$PATH"; pacman -S --needed --noconfirm mingw-w64-x86_64-toolchain mingw-w64-x86_64-mpg123 mingw-w64-x86_64-gtk2 mingw-w64-x86_64-libogg mingw-w64-x86_64-libvorbis mingw-w64-x86_64-lame mingw-w64-x86_64-pkg-config nasm yasm make base-devel autoconf automake libtool'
+
+      - name: Install llvm-mingw for ARM64 cross-compilation
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $llvmMingwVersion = "20250114"
+          $url = "https://github.com/mstorsjo/llvm-mingw/releases/download/$llvmMingwVersion/llvm-mingw-$llvmMingwVersion-ucrt-x86_64.zip"
+          Invoke-WebRequest -Uri $url -OutFile "$env:TEMP\llvm-mingw.zip"
+          Expand-Archive -Path "$env:TEMP\llvm-mingw.zip" -DestinationPath "C:\llvm-mingw-extract"
+          Move-Item -Path "C:\llvm-mingw-extract\llvm-mingw-$llvmMingwVersion-ucrt-x86_64\*" -Destination "C:\llvm-mingw" -Force
+          Write-Host "llvm-mingw installed to C:\llvm-mingw"
+
       - name: Clone repository
         uses: actions/checkout@v4
         with:
@@ -78,3 +90,4 @@ jobs:
           removeArtifacts: true
           artifacts: "artifacts/**/*.nupkg"
           token: ${{ secrets.GITHUB_TOKEN }}
+