Fix Python macos x86 build

[mlondschien]

No description provided.

[mlondschien]

@xhochy
in ac6c776, the macos universal2 build for python 3.8 failed with

         error[E0463]: can't find crate for `core`
          |
          = note: the `x86_64-apple-darwin` target may not be installed
          = help: consider downloading the target with `rustup target add x86_64-apple-darwin`

I thought universal2 was aarch?

I added a line to install the x86_64-apple-darwin target for the universal2 builds. Now the Python 3.13 build test stage fails with

    × Preparing metadata (pyproject.toml) did not run successfully.
    │ exit code: 1
    ╰─> [2 lines of output]
        
        meson-python: error: Multi-architecture builds are not supported but $ARCHFLAGS='-arch arm64 -arch x86_64'
        [end of output]

Before I simply don't build for Python 3.13: Is there something I am misunderstanding here?

[xhochy]

universal2 is x86 and aarch64 at the same time. I wouldn't build these wheels as they are quite heavy and barely used if you provide wheels for the architectures separately already.

[mlondschien]

Thanks @xhochy !