More attempts to get GDAL 2.3.2 pinned

[hobu]

We still aren't succeeding at getting things to pin.

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.

[msarahan]

I think the bit that you are missing is that conda-build tries to figure out which variables are "used" by matching names. libgdal != gdal. In this instance, you can force conda-build to match it by explicitly adding a jinja2 variable, like:

requirements:
  host:
    - libgdal  {{ gdal }}

More in the conda-build docs at https://conda.io/docs/user-guide/tasks/build-packages/variants.html