Add archspec packages for x86_64

[chrisburr]

When dependent packages require archspec the bot fails to solve despite the situation being okay. For example: https://conda-forge.org/status/migration/?name=root_base6328

This fixes this by always including the x86_64_v3 virtual package when solving for x86_64. We could think of including other virtual packages but I'm not sure if it's worth it.

[beckermr]

The virtual packages are written to disk as a separate channel here: https://github.com/chrisburr/conda-forge-feedstock-check-solvable/blob/fake-archspc/conda_forge_feedstock_check_solvable/virtual_packages.py#L114

We need to add the archspec version / names we support as globals in utils.py and then write them in the same way.

Also we'll need to add tests.

[chrisburr]

I thought I had tried that and it didn't work I'll try again

[chrisburr]

What do you think about doing the opposite and setting them all properly instead of making a fake channel?

[beckermr]

The fake channel is there so that we can use mamba as the solver backend in addition to rattler. We are approaching a time where mamba support can be removed (and it is currently broken in the tests), but we have not reached that point yet IMHO.

[chrisburr]

Given the mamba support will likely be removed how about I port it over and make the fake channel mamba specific?

[beckermr]

That'd be fine as long as we have a test that ensure the virtual packages end up the same for each solver.

[beckermr]

I pushed changes to at least get the mamba tests to run even if they fail.

[chrisburr]

Having thought about it more I think the virtual_package_repodata approach is better as it allows the solver to have multiple of the same virtual package with different versions.

[beckermr]

LGTM and thank you!