Work around missing appveyor component

Author: Matthew Orlando

appveyor.yml

@@ -29,6 +29,10 @@ cache:
   - .cache/obs_deps.zip
 
 # Scripts
+
+init:
+- ps: & 'C:\Program Files (x86)\Microsoft Visual Studio\Installer\vs_installer.exe' --quiet --wait --norestart --add Microsoft.VisualStudio.Component.VC.Llvm.ClangToolset | Out-Null
+
 install:
 - cmd: ci/win/install.cmd