CI: Update WoA job to use LLVM 20.1.8 and avoid stray preinstalled LLVM19 (#5411)

* Update to 20.1.8

* fix PATH to avoid the obsolete LLVM19 that appeared in the preinstalled msvc folder hierarchy

.github/workflows/windows_arm64.yml

@@ -4,11 +4,9 @@ on:
   push:
     branches:
       - develop
-      - release-**
   pull_request:
     branches:
       - develop
-      - release-**
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
@@ -28,10 +26,12 @@ jobs:
       - name: Install LLVM for Win-ARM64
         shell: pwsh
         run: |
-          Invoke-WebRequest https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.6/LLVM-20.1.6-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
           Start-Process -FilePath ".\LLVM-woa64.exe" -ArgumentList "/S" -Wait
           echo "C:\Program Files\LLVM\bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
-
+          #dir "C:\Program Files\LLVM\include\flang"
+          #rmdir /Q /S "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Tools/Llvm/ARM64"
+          
       - name: Install CMake and Ninja for Win-ARM64
         shell: pwsh
         run: |
@@ -47,6 +47,8 @@ jobs:
         shell: cmd
         run: |
           CALL "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsarm64.bat"
+          set PATH=C:\Program Files\LLVM\bin;%PATH%
+          
           mkdir build
           cd build
           cmake .. -G Ninja ^