microarch example: List at least one microarch_level

[stuarteberg]

Avoids a (presumed) bug in conda-build, as described here.

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[isuruf]

Is there a conda-build issue with a reproducer?

[stuarteberg]

Is there a conda-build issue with a reproducer?

Unfortunately, no. I made a brief attempt at creating a minimal reproducer, but did not succeed.

But conda-build was clearly doing something wrong with our build. (It had two of us feedstock maintainers scratching our head.) In lieu of a proper fix, we might spare some folks a headache if they start with an example config that is known to work.

[jaimergp]

Quoting @mbargull's comment:

As far as I can tell, the only explanation is that conda-build has a bug.

It is probably not a bug, but the (IMO, unfortunate) feature of conda-build in that it searches for uses of environment variable corresponding to the variant entries in build scripts and thus considers microarch_level as a "used" due to the ${microarch_level} in your script. It might suffice to just say ${microarch_level:-1} instead in the build script to avoid it.

[isuruf]

Thanks