MacOS Catalina: Slow by Design?

The way to avoid this behavior is to staple the notarization ticket to your bundle (or dmg/pkg), i.e. "/usr/bin/stapler staple <path>." Otherwise, Gatekeeper will fetch the ticket and staple it for the user on the first run.

(I'm the author of xcnotary [1], a tool to make notarization way less painful, including uploading to Apple/polling for completion/stapling/troubleshooting various code signing issues.)

[1] https://github.com/akeru-inc/xcnotary

The "Developer Tool" pane in System Prefs, Security, Privacy is the same power. Drag anything into that list you'd like to grant the same privilege (such as xcodebuild). This is inherited by child processes as well.

The point of this is to avoid malware packing bits of Xcode with itself and silently compiling itself on the target machine, thus bypassing system security policy.