[cmake-developers] iOS support

[Bill Hoffman]

> That said it would be really cool to beef up the xcode support enough to
> be able to create an actual ios app.  I have not dug into that enough.
> Should be able to do most of it with CMAKE_XCODE_ATTRIBUTE.     I will
> look into this try_compile COPY_FILE issue today and get back to the list.
>
> It would be great if you could get an example/Test in place that builds
> an app for a device and works with Xcode and for a stretch goal also
> works with makefiles or ninja.
>
Couple of more things.

Much of the stuff found in these toolchains:
https://github.com/Kitware/VTK/blob/master/CMake/ios.toolchain.xcode.cmake
https://github.com/Kitware/VTK/blob/master/CMake/ios.simulator.toolchain.cmake
https://github.com/Kitware/VTK/blob/master/CMake/ios.device.toolchain.cmake
Should be in Platform files.  If we created ios platform files we could 
remove most of the stuff from those toolchain files.  This would be a 
great thing to work on.

Also, Robert M reminded me that there is a test that could be extended 
as this stuff is developed:

https://github.com/Kitware/CMake/tree/master/Tests/iOSNavApp ) as it
already builds targeting the iphone simulator.

-Bill