Build platform of your Electron app that is currently being signed.
Allowed values: darwin (Direct Download App), mas (Mac App Store).
This reflects the platform that @electron/osx-sign resolved for this run, which is
useful when it was auto-detected from the presence of Squirrel.framework rather than
passed explicitly.
Context passed as the second argument to the OnlySignOptions.optionsForFile | optionsForFile callback. This object can grow over time, so destructure only the properties you need.