CI: move py39 build to conda #33948
- [x] closes #33948


very nice ping on green-ish (some builds are failing for unrelated reasons) This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. i think this could work now, @fangchenli can you merge master and let's see  very nice @fangchenli  @meeseeksdev backport 1.1.x Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
$ git checkout 1.1.x
$ git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
$ git cherry-pick -m1 0734fd852e4db2a969696fc4ef37725e0f11104f
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
$ git commit -am 'Backport PR #37039: CI: move py39 build to conda #33948'
```

4. Push to a named branch :

```
git push YOURFORK 1.1.x:auto-backport-of-pr-37039-on-1.1.x
```

5. Create a PR against branch 1.1.x, I would have named this PR:

> "Backport PR #37039 on branch 1.1.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                