platform = arm64 or universal2 both create x86_64 wheels

[MarkWieczorek]

When using multibuild to create macOS wheels for the project shtools, it appears that only "x86_64" wheels are supported for macos. In particular

        os: [macos-latest]
        include:
          - os: macos-latest
            platform: universal2

and

        os: [macos-latest]
        include:
          - os: macos-latest
            platform: arm64

both generate macos wheels with names like -macosx_10_9_x86_64.whl

Here are the CI builds for the two cases

• arm64: https://github.com/SHTOOLS/build-shtools/actions/runs/5022654093
• universal2: https://github.com/SHTOOLS/build-shtools/actions/runs/5003886586

[radarhere]

I know that they aren't completely unsupported, as pillow-wheels is able to successfully generate arm64 wheels - https://github.com/python-pillow/pillow-wheels/actions/runs/4957968985/jobs/8870274740#step:4:7795

There is a PR open that builds universal2 wheels - python-pillow/pillow-wheels#365, https://github.com/python-pillow/pillow-wheels/actions/runs/4625188095/jobs/8180714113#step:4:15273