[feature] Allow overriding CMAKE_OSX_ARCHITECTURES for CMakeToolchain generator

[ssrobins]

I'm building an iOS app that supports armv7 and arm64 architectures for maximum device compatibility. I currently accomplish that with the cmake generator by adding this to my conanfile.py:
cmake.definitions["CMAKE_OSX_ARCHITECTURES"] = "armv7 arm64"

The conan package setting is arch=armv7, which is the best I can do without multiarch, but it gets the job done.

With the CMakeToolchain generator, the equivalent setting doesn't do anything:
tc.variables["CMAKE_OSX_ARCHITECTURES"] = "armv7 arm64"

I think the 'right way' to support this is to allow multiple architectures on platforms such as iOS and Android that allow that in the build. But if that's not feasible within the Conan 2.x release timeframe, being allowed to override CMAKE_OSX_ARCHITECTURES would give us the same capability we currently have in Conan 1.x.

[ssrobins]

Any updates or suggested workarounds?

[memsharded]

Hi @ssrobins

Yes, the CMAKE_OSX_ARCHITECTURES is defined by the CMakeToolchain, the AppleBlock.
You can override its value with (check https://docs.conan.io/en/latest/reference/conanfile/tools/cmake/cmaketoolchain.html#extending-and-customizing-cmaketoolchain):

def generate(self):
    tc = CMakeToolchain(self)
    tc.blocks["apple_system"].values["cmake_osx_architectures"] = "...."
    tc.generate()

[ssrobins]

Thanks, this works perfectly! I'm now completely converted to CMakeDeps/CMakeToolchain and mostly ready for Conan 2.0 :)
https://github.com/ssrobins/conan-recipes
Feel free to close this, if you like.

[memsharded]

Excellent! Thanks for following up and reporting!