add_library: mention that Xcode requires a real source file
The docs mentioned that it happened, but not when. Mention Xcode since it is the culprit today.
See #16524 (closed).
Cc: @thughes
The docs mentioned that it happened, but not when. Mention Xcode since it is the culprit today.
See #16524 (closed).
Cc: @thughes