Add ARM support

[Timmmm]

Also minor formatting cleanups and simplifications, and I fixed a typo bi->bin typo.

Fixes #8

[markusstephanides]

Hi what else needs to happen so this can be merged?

[Timmmm]

It just needs review. I've been using it fine for a while.

In the mean time you can use my fork like this:

    - name: Set up MacOS Cross Compiler
      uses: Timmmm/setup-osxcross@v3
      with:
        osx-version: "12.3"

I also updated the actions/cache version so it doesn't trigger a CI warning (and they're due to remove the old version in November).