Use `Meta/serenity.sh build lagom MacPDF` to build, and either of
`open Build/lagom/bin/MacPDF.app` or
`Build/lagom/bin/MacPDF.app/Contents/MacOS/MacPDF` to run.
Xcode used to insert a bunch of things to Info.plist. Now it can
no longer do that, so manually put them there
Automatic termination means that the app no longer shows up as
opened in the doc when the last Window is closed, but it's actually
still running and opens immediately when clicked again.
Sudden termination means that the app can close quickly on logout.
I think it means the runtime just calls _exit() and assumes all
data is saved continuously.