fixup! Add notarization support

fixup! fixup! Add notarization support

README.md

@@ -266,6 +266,9 @@ it to the login keychain see the web page [Customizing the Notarization Workflow
 
 `asc_provider` option is only needed when a user account is associated with multiple providers.
 
+Xcode 10 (or newer) is **required**.  If you have more than one version of Xcode installed on your Mac,
+be sure to use the xcode-select utility to choose the appropriate version: `sudo xcode-select -s /path/to/Xcode10.app`
+
 Notarization process is described on Apple web page [Customizing the Notarization Workflow](https://developer.apple.com/documentation/security/notarizing_your_app_before_distribution/customizing_the_notarization_workflow).
 
 `munki-pkg` basically runs two commands: