use LLVM 20.1.8 on win-arm64 builds

Author: mattip

.github/workflows/windows-arm.yml

@@ -48,7 +48,13 @@ jobs:
 
     - name: Download and install LLVM installer
       run: |
-        Invoke-WebRequest https://github.com/llvm/llvm-project/releases/download/llvmorg-19.1.5/LLVM-19.1.5-woa64.exe -UseBasicParsing -OutFile LLVM-woa64.exe
+        Invoke-WebRequest https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.8/LLVM-20.1.8-woa64.exe -UseBasicParsing -OutFile LLVM-woa64.exe
+        $expectedHash = "7c4ac97eb2ae6b960ca5f9caf3ff6124c8d2a18cc07a7840a4d2ea15537bad8e"
+        $fileHash = (Get-FileHash -Path "LLVM-woa64.exe" -Algorithm SHA256).Hash
+        if ($fileHash -ne $expectedHash) {
+            Write-Error "Checksum verification failed. The downloaded file may be corrupted or tampered with."
+            exit 1
+        }
         Start-Process -FilePath ".\LLVM-woa64.exe" -ArgumentList "/S" -Wait
         echo "C:\Program Files\LLVM\bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append