Clean /Users/qt/Library/Caches of non-virtualized arm Mac CI machines

The machines "macos-12-arm64-developer-build-tests" and "macos-12-arm-on-arm64-tests" do not have QT_DISABLE_SHADER_DISK_CACHE set which means that shaders will be cached and read from disk. The problem is that changing our built-in shaders in a commit can make the cached shader incompatible making it impossible to make certain changes. For instance: https://codereview.qt-project.org/c/qt/qtquick3d/+/558887 does not pass CI. I believe this is the issue since this https://codereview.qt-project.org/c/qt/qtquick3d/+/559703 patch works which is the same as the above one except it has shader disk cache disabled in the code, but since VNC does not work on these machines I haven't looked into it deeper.

Solution is to run "rm -rf /Users/qt/Library/Caches" after each job.