aarch64 and ppc64le

[isuruf]

Checklist

• Used a fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[jakirkham]

We were discussing moving to ruamel.yaml for conda. ( conda-forge/conda-feedstock#81 ) That said, feel free to go ahead with this short-term if it helps move things forward.

[isuruf]

Merging for now to get this going

[mbargull]

Well, looks like there was an unannounced breaking change in conda/conda@86cb184#diff-aa5c1e6732e4802903e91fe909341fd0L380.
Fixing the test is as simple as

-check_call('conda config --add channels _test_channel_'.split(), env=env)
+check_call('conda config --add channels _test_channel_'.split() + ['--file={}'.format(condarc_path)], env=env)

It's still ugly to have these tests here, though, of course.
We should revisit the downstream testing thing. But I don't know how that handles chicken-egg-problems, e.g., testing ruamel{.,_}yaml built for python=3.8 when conda isn't yet available for that...