pin to 18.1.0

Author: savannahostrowski

.github/workflows/jit.yml

@@ -120,7 +120,7 @@ jobs:
         if: runner.os == 'Windows' && matrix.architecture == 'ARM64'
         run: |
           choco upgrade llvm -y
-          choco install llvm --allow-downgrade --no-progress --version ${{ matrix.llvm }}
+          choco install llvm --allow-downgrade --no-progress --version ${{ matrix.llvm }}.1.0
           ./PCbuild/build.bat --experimental-jit ${{ matrix.debug && '-d' || '' }} -p ${{ matrix.architecture }}
 
       - name: Native macOS