Add kext caveat to Casks (#41311)

* openzfs

* virtualbox

* little-snitch

Casks/little-snitch.rb

@@ -50,6 +50,7 @@ cask 'little-snitch' do
       rmdir: '/Library/Application Support/Objective Development'
 
   caveats do
+    kext
     reboot
   end
 end

Casks/openzfs.rb

@@ -40,4 +40,8 @@ cask 'openzfs' do
                       executable: "#{staged_path}/Docs & Scripts/uninstall-openzfsonosx.sh",
                       sudo:       true,
                     }
+
+  caveats do
+    kext
+  end
 end

Casks/virtualbox.rb

@@ -28,4 +28,8 @@ cask 'virtualbox' do
                '~/Library/Saved Application State/org.virtualbox.app.VirtualBoxVM.savedState',
              ],
       rmdir: '~/VirtualBox VMs'
+
+  caveats do
+    kext
+  end
 end