Install pkg-config file on Windows

[hattne]

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• 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-webservices]

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.

[hattne]

Pipelines failed on Python import for Linux-Python 3.8 on aarch64 and ppc64le, possibly because runtime path on compiled Python module was not set. Is this make -j 2 tripping itself up?

@conda-forge-admin, please restart ci

[hattne]

Fails consistently: same architecture–Python combination.

Actually looking at the logs this time: import fails (and runtime paths cannot be set) because modules are not built. Modules are not built because CMake bails out due to version mismatch (3.8.16 interpreter with 3.8.15 libs). As far as I can see, there are no aarch64 or ppc64le packages for Python-3.8.16, so conda uses linux64 ones instead.

[hattne]

I realize there are some gratuitous changes in this PR which could be cleaned up, but is there a more fundamental reason preventing this from being merged? I believe having something like this would make building packages against nlopt a tad easier.

[hattne]

Merged upstream, stevengj/nlopt#534; will wait for next release.