Use the correct file location for `SoftwareUpdate` plist.

[emmceemoore]

I'm not sure if something changed in macOS or if this ever worked (@treffynnon, who originally added this might know 🤷).

I've tried both true and false for system.defaults.SoftwareUpdate.AutomaticallyInstallMacOSUpdates and nothing seems to change in System Settings as I would have expected it to.

I did discover that there's a /Library/Preferences/com.apple.SoftwareUpdate.plist on my mac which does appear to reflect the Software Update settings.

$ plutil -p /Library/Preferences/com.apple.SoftwareUpdate.plist

{
  "AutomaticallyInstallMacOSUpdates" => 0
  "LastAttemptBuildVersion" => "14.5 (23F79)"
  "LastAttemptSystemVersion" => "14.5 (23F79)"
  "LastBackgroundSuccessfulDate" => 2024-07-02 01:19:50 +0000
  "LastFullSuccessfulDate" => 2024-07-02 16:26:36 +0000
  "LastRecommendedMajorOSBundleIdentifier" => ""
  "LastRecommendedUpdatesAvailable" => 0
  "LastResultCode" => 2
  "LastSessionSuccessful" => 1
  "LastSuccessfulDate" => 2024-07-02 16:27:14 +0000
  "LastUpdatesAvailable" => 0
  "PrimaryLanguages" => [
    0 => "en-US"
    1 => "en"
  ]
  "RecommendedUpdates" => [
  ]
}

I was able to write to this file and get the expected results in System Settings.

$ sudo defaults write /Library/Preferences/com.apple.SoftwareUpdate.plist AutomaticallyInstallMacOSUpdates -bool true

This leads me to believe that the proposed changes will work as expected (at least on a MacBook Pro with an Apple M3 Max running Sonoma 14.5 😅).