Build an executable as an application bundle on Mac OS X.

When this property is set to true the executable when built on Mac OS X will be created as an application bundle. This makes it a GUI executable that can be launched from the Finder. See the MACOSX_BUNDLE_INFO_PLIST target property for information about creation of the Info.plist file for the application bundle. This property is initialized by the value of the variable CMAKE_MACOSX_BUNDLE if it is set when a target is created.