[SDL2] cmake: ios/tvos support

[madebr]

This backports SDL3 CMake changes to support building SDL2 for ios/tvos.

testgles.c, testgles2.c and testgles2_sdf.c fail to build.
I hope an Apple person takes care of those.

Description

Existing Issue(s)

Fixes #10526

[yorickreum]

Build seems to fail because Apple deprecated OpenGLES, best way forward might just be to define GLES_SILENCE_DEPRECATION.

[madebr]

Build seems to fail because Apple deprecated OpenGLES, best way forward might just be to define GLES_SILENCE_DEPRECATION.

How does SDL3 handle this? I cannot find find GLES_SILENCE_DEPRECATION in the main branch.

[yorickreum]

Build seems to fail because Apple deprecated OpenGLES, best way forward might just be to define GLES_SILENCE_DEPRECATION.

How does SDL3 handle this? I cannot find find GLES_SILENCE_DEPRECATION in the main branch.

That is an excellent question ... I do not know but would be very curious, @slouken do you maybe know how SDL is dealing with Apples deprecation of OpenGL?

[yorickreum]

So, I checked https://github.com/libsdl-org/SDL/pull/9465/files/7aed78b825d193b55de36b500d146e991d2cc59d and see that check_c_compiler_flag(-Wno-error=deprecated-declarations HAVE_WNO_ERROR_DEPRECATED_DECLARATIONS) was explicitly added for macOS only, to turn those errors into warnings only and make testgles work ... this might explain why it's compiling.

I still do feel like add_compile_definitions(GLES_SILENCE_DEPRECATION) for iOS is the way cleaner solution, since we are explicitly silencing the GLES deprecation, not neglecting just all deprecation warnings...

[yorickreum]

https://github.com/libsdl-org/SDL/blob/efdcfef4b94c41229b92633e184b17b7f3c4d01c/CMakeLists.txt#L590C1-L595C10

[madebr]

Thanks @yorickreum , I applied your suggestion (GLES_SILENCE_DEPRECATION).

Can you explain why linking the tests fails (and provide a fix) on ios/tvos?

Undefined symbols for architecture arm64:
  "_main", referenced from:
      <initial-undefines>
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[yorickreum]

Thanks! Just from the error message, I‘d assume it’s trying to link something that was compiled for the wrong architecture (e.g. just macOS not iOS).
I can maybe dig deeper later.

[madebr]

Thanks! Just from the error message, I‘d assume it’s trying to link something that was compiled for the wrong architecture (e.g. just macOS not iOS). I can maybe dig deeper later.

I forgot about SDL2main :)