gha/add llvmlite osx 64 conda builder

[swap357]

this PR adds osx64 conda builder workflow for llvmlite.
It needs same fixes for osx-64 as llvmdev workflow PR - https://github.com/numba/llvmlite/pull/1167/files
This PR is a superset of #1167

[esc]

I am testing the llvmlite_osx-64_conda_builder using the ID 14313666110 from https://github.com/numba/llvmlite/actions/runs/14313666110 at:

https://github.com/esc/llvmlite/actions/runs/14333921715

however, it seems there is an issue trying to download the artifact:

Run actions/download-artifact@v4
  with:
    name: llvmdev_osx-64
    path: llvmdev_conda_packages
    run-id: 14[3](https://github.com/esc/llvmlite/actions/runs/14333921715/job/40176074824#step:6:3)13666110
    repository: esc/llvmlite
    github-token: ***
    merge-multiple: false
  env:
    INPUT_RUN_POST: true
    CONDA: /Users/runner/miniconda3
Downloading single artifact
Error: Unable to download artifact(s): Not Found

sadly I don't know what the issue is here. Could it be that I need to have run the llvmdev in my fork also?

[esc]

Tried a build of llvmdev on main of the esc/llvmlite fork:

https://github.com/esc/llvmlite/actions/runs/14334012418

The used the workflow ID 14334012418 to launch:

https://github.com/esc/llvmlite/actions/runs/14337845023

[esc]

@swap357 thank you for the pushes, I will re-review this now.

[esc]

Testing protocol and results:

a) merged this PR to esc/llvmlite@main: esc@0b15a08

b) used a GHA produced llvmdev from https://github.com/esc/llvmlite/actions/runs/14334012418

c) ran: https://github.com/esc/llvmlite/actions/runs/14354807935

This was green. The code in this PR is fine. But it can not yet be merged until the following PRs are also green:

#1187

numba/numba#10023

and the PR for numba osx-64 wheels that has ye to appear.

As a result I will label this as "waiting on CI".

[seibert]

#1187 has been merged. It looks like numba/numba#10023 is also working, and I don't know if we need to wait for the numba osx-64 wheel PR to be created before this one is. I'm going to keep this all moving forward, and if we need to open some smaller PRs to fix up issues found later, we can do that.

esc's requested change has been made, but he's not available this week to update his review.

[seibert]

The changes @esc requested seem to have been made. Approving.

[swap357]

numba wheel builder PR has been created and tested here - numba/numba#10038