Attempted fix for missing install name for mumps libraries on osx

[jcapriot]

Checklist

• Used a personal 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.

closes #103

I don't have a lot of experience building mumps, but looking through the downloaded files, this is where I would expect the issue is coming from.

[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.

[jcapriot]

Looks like #102 makes this same fix (in addition to the int-header issue)

[minrk]

Thanks! Yeah, I found this in #102 because it also re-enables the tests that hadn't been there. Other than weird openmpi cuda things, #102 should get things ready for 5.6, as far as I can tell.

[jcapriot]

close in favor of #102