Try Vinod's fix.

Author: matthew-brett

.github/workflows/windows-arm.yml

@@ -32,6 +32,21 @@ jobs:
     - name: Setup visual studio
       uses: microsoft/setup-msbuild@v2
 
+    - name: Download LLVM installer for woa64
+      run: |
+        curl -L -o LLVM-woa64.exe https://github.com/llvm/llvm-project/releases/download/llvmorg-19.1.5/LLVM-19.1.5-woa64.exe
+
+    - name: Install LLVM silently
+      shell: pwsh
+      run: |
+        Start-Process -FilePath ".\LLVM-woa64.exe" -ArgumentList "/S" -Wait
+
+    - name: Add LLVM to PATH
+      shell: pwsh
+      run: |
+        $llvmPath = "C:\Program Files\LLVM\bin"
+        echo "$llvmPath" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+
     - name: Build
       run: |
         git submodule update --init --recursive