sdl_mixer: link AudioUnit only on macOS

[kambala-decapitator]

Summary

Changes to recipe: sdl_mixer/2.8.0

Motivation

Fixes linker error in iOS project that consumes sdl_mixer

Details

AudioUnit framework is available only for macOS, on iOS you'd receive

ld: framework 'AudioUnit' not found
clang: error: linker command failed with exit code 1 (use -v to see invocation)

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[AbrilRBS]

Thanks for the clear message error, we appreciate it! :)

[AbrilRBS]

Im trying to understand one thing:

• Upstream's CMakeLists has this line target_link_libraries(SDL2_mixer PRIVATE -Wl,-framework,AudioToolbox -Wl,-framework,AudioUnit -Wl,-framework,CoreServices) with only an if(APPLE) condition
• https://developer.apple.com/documentation/audiounit/ lists OS 2.0+ iPadOS 2.0+ Mac Catalyst 13.0+ macOS 10.0+ tvOS 9.0+ visionOS 1.0+

Which confuses me a bit as to how this would be working upstream (Maybe they just dont test for ios specifically?) and if there are other apple os that would need this framework besides just macos

[kambala-decapitator]

Yes, that's rather strange. I've just checked in a test iOS project in Xcode: you can select AudioUnit from the list of system frameworks, but on build you receive linker error:

This seems to be the explanation: https://stackoverflow.com/a/14120936

will check upstream behavior later today.