Xcode: OSX_DEPLOYMENT_TARGET should depend on target architecture
When building a CMake project for multiple architectures (x86_64 and arm64) on Mac it should be possible to set the minimum macOS version depending on the architecture.
The first macOS version ever supporting the Apple Silicon (ARM) architecture was macOS 11.0. Accordingly all sources compiled for Apple Silicon need to be compiled with
'-target arm64-apple-macos11.0'. However, the x86_64 variant in the universal binary should be able to support macOS versions down to 12.0. Currently the OSX_DEPLOYMENT_TARGET is set unconditionally, which either:
- leads to compilation errors when building for arm64 against the 11.0 or higher SDKs
- prevents x86_64 code to run on a version older than 11.0
It should therefore be possible to specify the macOS target version based on the target architecture.