The YARP_DISABLE_OSX_BUNDLES option should be removed

[drdanz]

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On macOS, executables are built twice, to support macOS bundles All sources are actually compiled twice, unless the YARP_DISABLE_OSX_BUNDLES option is enabled. With recent CMake versions we have OBJECT libraries, that could be used to allow the normal application and the bundle to share the same object files, avoiding to build them twice.