@electron-forge/maker-pkg builds .pkg files for macOS. These are used to upload your application to the Mac App Store or just as an alternate distribution method for macOS users. You can only build the Pkg target on macOS machines while targeting the darwin or mas platforms.
Configuration options are documented in MakerPkgConfig.
{
name: '@electron-forge/maker-pkg',
config: {
keychain: 'my-secret-ci-keychain'
}
}